LIBRARY 

UNIVERSITY  OF  CALIFORNIA. 
JAN   16    1893 


^Accessions  No.      G~&~$lL  ,.  Class 


Series  of  /IDofcern  Jpbilosopfoers. 

Edited  by  E.  Hershey  Sneath,  Ph.D. 


DESCARTES  by  PROF.  H.  A.  P.  TORREY  of  the 

University  of  Vermont.* 
SPINOZA  by  PROF.  GEO.  S.  FULLERTON  of  the 

University  of  Pennsylvania.* 
LOCKE  by  PROF.  JOHN  E.  RUSSELL  of  Williams 

College.* 
BERKELEY  by  EX-PRESIDENT  NOAH  PORTER 

of  Yale  University. 
HUME  by    PROF.  H.  AUSTIN  AIK1NS  of  Trinity 

College,  N.  C. 

REID   by  E.  HERSHEY   SNEATH  of  Yale  Uni- 
versity.* 
KANT    by   PROF.   JOHN   WATSON  of   Queen's 

University,  Canada.* 
HEGEL  by  PROF.  JOSIAH   ROYCE  of  Harvard 

University. 

*  Those  marked  with  an  asterisk  are  ready 


HENRY  HOLT  &  CO.,  PUBLISHERS, 

NEW  YORK. 


Series  of  flftobern  fcbilosopbers 

,Edited  by  E.  Hershey  Sneath,  Ph.D. 

THE 

PHILOSOPHY  OF  REID 

it 

AS  CONTAINED  IN  THE 

"INQUIRY  INTO  THE   HUMAN  MIND 

ON    THE    PRINCIPLES    OF 

COMMON   SENSE" 


WITH    INTRODUCTION  AND   SELECTED   NOTES 
BY 

E.    HERSHEY   SNEATH,   PH.D. 

Instructor  in  Philosophy  in  Yale  University 


NEW  YORK 

HENRY    HOLT    AND    COMPANY 
1892 


15/5-3 
_T3 


COPYRIGHT,  1892, 

BY 
HENRY   HOLT  &  CO. 


PREFACE. 


AFTER  careful  consideration,  it  seemed  better  to  me, 
and,  at  the  same  time,  to  be  consistent  with  the  idea 
of  the  "  Series"  of  which  this  book  is  a  member,  to 
present  Reid's  Philosophy  in  an  edition  of  the  "  In- 
quiry," rather  than  in  a  book  of  extracts  taken  from 
the  "  Inquiry"  and  the  "  Intellectual  Powers."  The 
substance  of  Reid's  Philosophy  is  contained  in  his 
theory  of  perception  and  his  doctrine  of  common 
sense.  Herein,  too,  lies  his  historical  significance. 
The  "  Inquiry"  contains  all  that  is  essential  for  an 
understanding  of  Reid's  views  on  these  subjects,  and 
presents  it  in  a  comparatively  brief  form.  By  omit- 
ting Sees.  IX-XIX  (pp.  199-287),  which  can  be  easily 
spared,- the  subject-matter  will  be  brought  within  the 
limits  prescribed  by  the  "  Series. "  The  sections  re- 
ferred to  above  will  be  found  interesting,  especially 
when  studied  in  connection  with  Berkeley's  famous 
*'  Theory  of  Vision," — hence  their  retention.  The 
text  of  this  edition  is  taken  from  Sir  Wm.  Hamilton's 
seventh  edition  of  Reid's  Works  (Edinburgh,  1872). 
The  most  important  notes  of  Hamilton,  as  well  as  his 
Index,  abridged,  have  been  retained.  The  "  Inquiry" 
affords  an  inviting  field  for  criticism,  but  the  limits  of 
the  Introduction  forbade  my  entering  upon  it. 

E.  H.  S. 
iii 


CONTENTS. 


PAGE 

BIOGRAPHICAL  SKETCH. i 

BIBLIOGRAPHY „ 7 

RELATION  OF  REID'S  PHILOSOPHY  TO  ITS  PHILOSOPHICAL 

ANTECEDENTS u 

THE  INFLUENCE  OF  REID'S  PHILOSOPHY  UPON  SUBSEQUENT 

PHILOSOPHIC  THOUGHT 47 

AN    INQUIRY    INTO   THE   HUMAN   MIND. 
DEDICATION 65 

CHAPTER  I.     INTRODUCTION. 

Section  I.  The    Importance  of   the   subject,  and  the  Means 

of  prosecuting  it 70 

II.  The  Impediments  to  our  knowledge  of  the  mind..     72 

III.  The  Present  State  of  this  part  of  philosophy.     Of 

Descartes,  Malebranche,  and  Locke 76 

IV.  Apology  for  those  philosophers 80 

V.  Of  Bishop  Berkeley;    the  "Treatise  of  Human 

Nature"  ;  and  of  Scepticism ,  81 

VI.   Of  the  ' '  Treatise  of  Human  Nature" 84 

VII.  The  system  of  all  these  authors  is  the  same,  and 

leads  to  Scepticism 86 

VIII.  We  ought  not  to  despair  of  a  better 87 

CHAPTER  II.     OF  SMELLING. 

Section  I.  The  Order  of   proceeding.     Of  the  medium  and 

organ  of  Smell 89 

II.  The  Sensation  considered  abstractly 90 

III.  Sensation   and    Remembrance,  natural   principles 

of  Belief 92 

v 


VI  CONTENTS. 

PAGE 

Section  IV.  Judgment  and  Belief  in  some  cases  precede  Sim- 
ple Apprehension 95 

V.  Two  Theories  of  the  Nature   of  Belief    refuted. 

Conclusions  from  wfiaThath  been  said 96 

VI.  Apology  for  metaphysical  absurdities.  Sensa- 
tion without  a  sentient,  a  consequence  of  the 
theory  of  Ideas.  Consequences  of  this  strange 

opinion 99 

VII.  The  conception  and  belief  of  a  sentient  being,  or 
Mind,  is  suggested  by  our  constitution.  The 
notion  of  Relations  not  always  got  by  Com- 
paring the  related  ideas 105 

VIII.  There  is  a  quality  or  virtue  in  bodies,  which  we 
call  their  Smell.     How  this  is  connected  in  the 

imagination  with  the  sensation. . .    109 

IX.  That  there  is  a  principle  in  human  nature,  from 
which  the  notion  of  this,  as  well  as  all  other 

natural  virtues  or  causes,  is  derived in 

X.  Whether    in   Sensation    the    mind   is  Active    or 

Passive 116 

CHAPTER  III.     OF  TASTING 118 

CHAPTER  IV.    OF  HEARING. 

Section  I.  Variety  of  Sounds.     Their    place    and    distance 

learned  by  Custom,  without  reasoning 122 

II.  Of  Natural  Language 124 

CHAPTER  V.    OF  TOUCH 

Section  I.  Of  Heat  and  Cold 129 

II.  Of  Hardness  and  Softness 131 

III.  Of  Natural  Signs 135 

IV.  Of  Hardness,  and  other  Primary  Qualities 139 

V.  Of  Extension 141 

VI.  Of  Extension 144 

VII.  Of  the  existence  of  a  Material  World 148 

VIII.  Of  the  Systems  of   Philosophers  concerning  the 

Senses 156 


CONTENTS. 


CHAPTER  VI.     OF  SEEING. 

Section  I.  The  excellence  and  dignity  of  this  faculty 162 

II.  Sight  discovers  almost  nothing  which  the   Blind 

may  not  comprehend.     The  reason  of  this 164 

III.  Of  the  Visible  Appearances  of  objects 169 

IV.  That  Colour  is  a  quality  of  bodies,  not  a  sensation 

of  the  mind 173 

V.  An  inference  from  the  preceding 177 

VI.  That  none  of  our  sensations  are  Resemblances  of 

any  of  the  qualities  of  bodies 181 

VII.  Of  visible  Figure  and  Extension 187 

VIII.  Some    Queries    concerning    Visible    Figure    an- 


swered. 


192 

IX.  Of  the  Geometry  of  Visibles 199 

X.  Of  the  Parallel  Motion  of  the  eyes 21 1 

XI.   Of  our  seeing  objects  Erect  by  inverted  images. .   215 
XII.  The  same  subject  continued 222 

XIII.  Of  seeing  objects  Single  with  two  eyes 238 

XIV.  Of  the  laws  of  vision  in  Brute  animals 246 

XV.  Squinting  considered  hypothetically 249 

XVI.  Facts  relating  to  Squinting 261 

XVII.  Of  the  effect  of  Custom  in  seeing  objects  Single. .   265 
XVIII.  Of  Dr.  Porterfield's  account  of  single  and  double 

vision 272 

XIX.  Of  Dr.   Brigg's  theory,  and  Sir  Isaac  Newton's 

conjecture  on  this  subject 276 

XX.  Of  Perception  in  general 287 

XXI.  Of  the  Process  of  Nature  in  perception 297 

XXII.  Of  the  Signs  by  which  we  learn  to  perceive  Dis- 
tance from  the  eye. 303 

XXIII.  Of  the  Signs  used  in  other  acquired  perceptions. . .   316 
XXIV    Of   the   Analogy   between    Perception,    and    the 

credit  we  give  to  Human  Testimony 320 

CHAPTER  VII.    CONCLUSION. 

Containing  Reflections  upon  the  opinions  of  Philosophers 

on  this  subject 338 

INDEX 363 


BIOGRAPHICAL  SKETCH. 

DUGALD  STEWART  truly  says,  that  the  life  of  Thomas 
Reid  "was  uncommonly  barren  of  those  incidents 
which  furnish  materials  for  biography."  His  life  was 
spent  in  comparative  quiet  and  retirement,  and  was, 
therefore,  not  replete  with  varied  incident.  He  was 
born  April  26th,  1710,  at  Strachan,  Kincardineshire, 
Scotland.  His  father  was  the  Rev.  Lewis  Reid,  a 
highly  respected  clergyman,  who  was  descended  from  a 
succession  of  ministers  of  the  Church  of  Scotland.  His 
mother,  Margaret  Gregory,  belonged  to  a  family  some- 
what distinguished  in  Scotland  for  their  scientific  attain- 
ments. Early  in  life  Reid  was  sent  to  the  parish  school 
of  Kincardine  where  he  spent  two  years.  From  the 
parish  school  he  went  to  Aberdeen,  where  he  received 
instruction  in  the  classics.  When  about  twelve  or  thir- 
teen years  of  age  he  entered  Marischal  College.  Here  he 
was  instructed  in  Philosophy  by  Dr.  George  Turnbull, 
who  undoubtedly  exerted  a  great  influence  upon  his  philo- 
sophical thinking.*  He  graduated  from  college  in  1726. 
Receiving  an  appointment  of  librarian  to  the  University, 
he  continued  his  connection  with  it  until  1736.  During 

*  Dr.  McCosh  says  that  Turnbull  exercised  a  greater  influence 
upon  Reid's  thinking  "  than  all  other  masters  and  writers  "  com- 
bined. "The  Scottish  Philosophy,"  pp.  95-106. 


at 
TJ5IVBESIT7 


2  BIOGRAPHICAL  SKETCH. 

this  period  he  devoted  much  of  his  time  to  the  study  of 
Mathematics.  Resigning  his  office  in  1736,  he  visited 
England  in  company  with  his  friend,  John  Stewart,  who 
afterward  held  the  chair  of  Mathematics  in  Marischal 
College.  They  visited  London,  Oxford  and  Cambridge, 
where  they  were  introduced  to  many  noted  literary  men. 
In  1737,  having  been  presented  "  to  the  living  of  New- 
Machar, "  by  King's  College,  Aberdeen,  he  entered  upon 
his  clerical  work.  The  early  part  of  his  ministerial  life  in 
this  parish  was  signalized  by  an  intense  hostility  to  him  on 
the  part  of  his  parishioners.  This  was  occasioned  specially 
by  the  aversion  which  his  people  had  to  the  law  of 
patronage.  Furthermore,  he  was  accustomed,  because 
of  his  modesty,  to  preach  the  sermons  of  Drs.  Tillotson 
and  Evans  instead  of  his  own.  This  practice  was  very 
offensive  to  the  people.  However,  despite  his  unpopu- 
larity, through  his  fidelity  to  the  interests  of  his  parish, 
and  his  amiability  of  disposition,  he  soon  ingratiated 
himself  into  the  good  will  and  affections  of  the  people. 
In  1740,  he  was  married  to  his  cousin,  Elizabeth  Reid, 
daughter  of  Dr.  George  Reid,  a  London  physician.  His 
wife  proved  a  great  help  to  him  in  his  work  at  New- 
Machar.  While  living  here,  "the  greater  part  of  his 
time,"  says  Dugald  Stewart,  "was  spent  in  the  most 
intense  study;  more  particularly  in  a  careful  examina- 
tion of  the  laws  of  external  perception,  and  of  the  other 
principles  which  fornT^the^  groundwork  of  human 
knowledge."*  In  1748,  his  first  publication  appeared. 
It  was  in  the  form  of  an  Essay,  published  in  the 
"Transactions"  of  the  Royal  Society  of  London,  and 

"Collected  Works,"  vol.  x,  p.  251. 


BIOGRAPHICAL    SKETCH.  3 

was  entitled,  "An  Essay  on  Quantity,  occasioned  by 
reading  a  Treatise  in  which  Simple  and  Compound 
Ratios  are  applied  to  Virtue  and  Merit. "  The  ' '  Trea- 
tise" to  which  Reid  alludes  was  Hutcheson's  "  Inquiry 
into  the  Origin  of  our  Ideas  of  Beauty  and  Virtue."  In 
this  "Treatise,"  Hutcheson  made  use  of  mathematical 
forms  in  illustrating  moral  subjects.  Whether  he  meant 
to  apply  mathematical  reasoning  to  such  subjects  may  be 
doubted.  Reid,  however,  was  aware  of  the  fact  that 
Pitcairn  and  Cheyne  had  applied  this  form  of  reasoning 
to  medicine,  and  he  felt  constrained  to  write  an  essay 
showing  what  rendered  a  subject  capable  of  mathemati- 
cal treatment. 

In  1752,  he  was  elected  Professor  of  Philosophy,  in 
King's  College,  Aberdeen.  Shortly  after  his  removal  to 
Aberdeen,  the  ' '  Aberdeen  Philosophical  Society  "  was 
founded,  principally  through  his  endeavors.  It  included 
among  its  members  such  men  as  Campbell,  Gerard, 
Beattie  and  John  Gregory.  *  While  connected  with  this 
society,  he  read  papers  which  contained  the  essential 
principles  of  the  "Inquiry."  In  1764,  he  published 
the  "  Inquiry  into  the  Human  Mind  on  the  Principles 
of  Common  Sense. "  Reid's  speculations  on  the  subjects 
treated  in  the  "  Inquiry  "  were  really  begun  in  1739,  on 
the  appearance  of  Hume's  "Treatise  of  Human  Nature." 
In  the  "Inquiry"  Reid  attempts  to  refute  the  scepti- 
cism of  Hume  by  attacking  the  "theory  of  ideas"  on 
which  he  thought  this  scepticism  to  be  founded.  Being 
thus  directed  against  the  sceptical  philosophy  of  Hume, 

*  Cf.  McCosh,  "The  Scottish  Philosophy,"  pp.  227-9,  for  an 
account  of  this  society. 


4  BIOGRAPHICAL    SKETCH. 

he  was  desirous  of  subjecting  his  manuscript  to  Hume's 
perusal,  so  as  not  to  misrepresent  his  philosophy  in  any 
particular.  He  was  enabled  to  do  this  through  the 
kind  services  of  Dr.  Blair,  a  mutual  friend.  After 
perusing  it  carefully,  Hume  wrote  to  Reid  the  following 
complimentary  words:  "By  Dr.  Blair's  means  I  have 
been  favored  with  the  perusal  of  your  performance, 
which  I  have  read  with  great  pleasure  and  attention. 
It  is  certainly  very  rare  that  a  piece  so  deeply  philo- 
sophical is  wrote  with  so  much  spirit,  and  affords  so 
much  entertainment  to  the  reader."*  In  1763,  Reid 
was  called  to  the  Professorship  of  Moral  Philosophy,  in  the 
University  of  Glasgow,  to  succeed  Adam  Smith,  who  had 
resigned.  He  accepted  the  call,  removing  to  Glasgow 
the  following  year.  In  the  University  he  lectured  on 
the  intellectual  and  active  powers  of  man,  and  on  natu- 
ral jurisprudence  and  politics.  Many  of  his  colleagues 
were  able  men  and  they  proved  to  be  a  great  inspiration 
to  him.  During  his  connection  with  the  University,  he 
published  "An  Account  of  the  Logic  of  Aristotle,"  as 
an  appendix  to  Lord  Kame's  "  Sketches  of  the  History 
of  Man."  In  1781,  he  retired  from  the  professorship, 
for  the  purpose  of  devoting  his  attention  to  the  comple- 
tion of  his  philosophical  works.  In  1785,  he  published 
the  ' '  Essays  on  the  Intellectual  Powers  of  Man, " — a 
more  elaborate  treatment  of  the  powers  of  the  mind 
.than  is  contained  in  the  "Inquiry."  In  1788,  he  pub- 
lished the  "Essays  on  the  Active  Powers  of  the  Human 
Mind,"  advocating  one  form  of  Intuitional  Ethics.  This 
was  the  last  work  of  his  published  during  his  lifetime. 

*  Stewart's  "  Collected  Works,''  vol.  x.,  p.  256. 


BIOGRAPHICAL  SKETCH.  5 

Reid  remained  an  active  student  almost  till  death. 
Among  the  most  important  efforts  of  the  closing  years 
of  his  life,  were  several  papers  written  probably  for 
a  literary  society  in  Glasgow.  These  were  entitled, 
"  Some  Observations  on  the  Modern  System  of  Ma- 
terialism," and  "A  Free  Discussion  of  the  Doctrines 
of  Materialism  and  Philosophical  Necessity."  One 
thing  marred  the  serenity  of  these  closing  years.  It 
was  the  death  of  his  wife,  with  whom  he  had  lived 
fifty-two  years.  Only  one  daughter,  Mrs.  Carmichael, 
of  a  large  family  of  children,  was  still  living.  She  was 
a  great  solace  to  him  in  his  old  age.  On  the  yth  of 
October,  1796,  after  a  brief  illness,  he  died. 

As  a  man,  Reid  was  modest,  sober,  sincere,  and  de- 
vout. He  was  modest  almost  to  diffidence.  Indeed, 
Dugald  Stewart  expresses  doubt  as  to  whether  Reid's 
modesty  would  have  permitted  him  to  publish  the 
"  Inquiry,"  had  he  not  been  encouraged  to  do  so  by 
his  friends.  His  soberness  and  earnestness  are  manifest 
both  in  his  life  and  writings.  Something  of  his  devout 
character  may  be  learned  from  a  confession  and  re-ded- 
ication of  himself  to  the  service  of  God,  during  his 
wife's  illness,  in  the  sixth  year  of  their  marriage.  It  is 
a  most  penitent  and  pathetic  confession  of  dereliction  of 
duty,  and  a  most  solemn  pledge  of  a  more  devoted  ser- 
vice to  God.* 

As  a  philosophical  thinker,  Reid,  if  not  profound, 
was,  at  least,  deeply  earnest  and  original.  Cousin 
thought  him  to  be  a  man  of  genius.  He  says:  "Yes, 
Reid  is  a  man  of  genius,  and  of  a  true  and  powerful 

*  Cf.  McCosh,  "  The  Scottish  Philosophy,"  pp.  199-200. 


6  BIOGRAPHICAL   SKETCH. 

originality;  so  we  said  in  1819,  and  so  we  say  in  1857, 
after  having  held  long  converse  with  mighty  systems, 
discovered  their  secret,  and  taken  their  measure."* 
McCosh  says:  "  He  has  not  the  mathematical  consecu- 
tiveness  of  Descartes,  the  speculative  genius  of  Leibnitz, 
the  sagacity  of  Locke,  the  spirituel  of  Berkeley,  or  the  de- 
tective skill  of  Hume;  but  he  has  a  quality  quite  as  valua- 
ble as  any  of  these,  even  in  philosophy;  he  has  in  per- 
fection that  common  sense  which  he  so  commends,  "f 
Sober  earnestness  and  originality  seem  to  be  his  merits 
as  a  philosophical  thinker.  His  earnestness  is  manifest 
in  his  anxious  endeavor  to  establish  the  reality  of  know- 
ledge, and  thus  to  save  philosophy  from  nihilistic 
scepticism.  His  originality  is  manifest  in  his  breaking 
away  from  the  "  theory  of  ideas"  which  he  had  accepted 
on  authority,  and  establishing  philosophy  upon  a  new 
basis. 

*  Quoted  by  McCosh,  "  The  Scottish  Philosophy,"  p.  193. 
f  Ibid.,  pp.  192-3. 


BIBLIOGRAPHY. 

/.   On  the  Life  of  Reid. 

Dugald  Stewart,  "Account  of  the  Life  and  Writings  of 
Thomas  Reid,  D.D.,"  <'  Collected  Works,"  ed.  by  Hamilton, 
Edinburgh,  1854-60,  vol.  x,  ch.  v.  Published  also  in 
"The  Works  of  Thomas  Reid,  D.D.,"  ed.  by  Hamilton, 
Edinburgh,  1872,  vol.  i,  pp.  1-35.  Cf.  Notes  A,  B,  C,  D, 
E,  F,  of  Hamilton,  appended  to  this  account. 

James  McCosh,  "The  Scottish  Philosophy,"  New  York, 
1874,  Art.  xxvi. 

//.   The  Works  of  Reid. 

Complete  Works  in  English:  "The  Works  of  Thomas 
Reid,  D.D.,  now  fully  collected,  with  Selections  from  his 
Unpublished  Letters.  Preface,  Notes,  and  Supplementary 
Dissertatipns,  by  Sir  William  Hamilton,  Bart.,"  etc.,  7th 
ed.,  Edinburgh,  1872,  2  vols.  In  French:  "  CEuvres  Com- 
pletes de  Thomas  Reid,  par  M.  Th.  Jouffroy,  avec  des 
Fragments  de  M.  Royer  Collard,"  Paris,  1828-9,  6  tomes. 

For  information  concerning  various  editions  of  individ- 
ual works  of  Reid,  cf.  N.  Porter,  "Ueberweg's  History 
of  Philosophy,"  translated  by  Geo.  S.  Morris,  New  York, 
1871-3,  vol.  ii,  Appendix  I,  pp.  396-7. 

///.  Books  of  Reference. 

In  English:  J,  Priestley,  "Examination  of  Dr.  Reid's 
Inquiry,"  etc.,  London,  1774. 

Dugald  Stewart,  "Collected  Works,"  ed.  by  Hamilton, 
Edinburgh,  1854-60,  vols.  i,  pp.  108-13;  v,  pp.  101-13. 

7 


8  BIBLIOGRAPHY. 

Th.  Brown,  '*  Inquiry  into  the  Relation  of  Cause  and 
Effect,"  3d  ed.,  Edinburgh,  1818.  "Lectures  on  the  Phi- 
losophy of  the  Human  Mind,"  Hallowell,  1829,  especially 
lectures  xxvi,  xxvii. 

Sir  Wm.  Hamilton,  "Lectures  on  Metaphysics,"  ed.  by 
Mansel  and  Veitch,  Edinburgh  and  London,  1870,  vol.  i, 
Appendix  I  (B),  vol.  ii,  lectures  xxi-xxiii.  Also,  "Preface, 
Notes  and  Supplementary  Dissertations,"  in  his  edition  of 
Reid's  "Works,"  referred  to  above. 

J.  F.  Ferrier,  "  Reid  and  the  Philosophy  of  Common 
Sense,"  "  Blackwood's  Magazine,"  1847;  the  same  in  Lec- 
tures, ed.  by  Grant  and  Lushington,  London,  1866,  vol.  ii, 

pp.  407-59- 

J.  Walker,  Notes  in  his  abridged  edition  of  Reid's  "  In- 
tellectual Powers  of  Man,"  Philadelphia,  1850. 

A.  C.  Fraser,  "Essays  in  Philosophy,"  Edinburgh,  1856, 
Essays  II  and  III. 

J.  McCosh,  "The  Scottish  Philosophy,"  New  York,  1874, 
pp.  192-227,  "  Realistic  Philosophy,"  New  York,  1887,  vol. 
ii,  pp.  173-81. 

Thomas  E.  Webb,  "  The  Veil  of  Isis,"  Dublin  and  Lon- 
don, 1885,  pp.  123-62. 

A.  Seth,  "  Scottish  Philosophy,"  Edinburgh  and  London, 
1885.  Article  on  Reid,  "  Encyclopaedia  Britannica,"  9th 
ed.,  vol.  xx. 

In  French:  Royer  Collard,  "Fragments  de  Royer  Col- 
lard,"  Jouffroy's  translation  of  Reid's  Works. 

V.  Cousin,  "  Philosophic  Ecossaise,"  Paris,  1846,  pp. 
185-281. 

Thomas  Jouffroy,  Preface  to  his  "  (Euvres  Completes  de 
Thomas  Reid,"  Paris,  1828-9. 

A.  Garnier,  "Critique  de  la  Philosophic  de  Thomas  Reid," 
Paris,  1840. 

J.  P.  A.  Remusat,  "Melanges,"  Paris,  1842. 

L.  Peisse,  Preface  to  "  Fragments  de  Philosophic,"  1840. 

In  German :  M.  Kappes,  "  Der  Common  Sense  bei 
Thomas  Reid,"  Munich,  1890. 

E.  Koenig,  "  Die  Entvvickelung  des  Causalproblems  von 
Cartesius  bis  Kant,"  Leipzig,  1888. 


BIBLIOGRAPHY.  9 

IV. 

Consult  also  the  following  writers  on  the  History  of 
Philosophy:  J.  D.  Morrel,  "  History  of  Modern  Philos- 
ophy," 2d  ed.,  London,  1847,  vol.  i,  pp.  281-94. 

N.  Porter,  "  Ueberweg's  History  of  Philosophy,"  trans- 
lated by  Geo.  S.  Morris,  New  York,  1871-3,  vol.  ii,  Appen- 
dix I,  pp.  394-403. 

F.  D.  Maurice,  "Moral  and  Metaphysical  Philosophy," 
London,  1873,  vol.  ii,  pp.  580-6. 

G.  H.   Lewes,  "  Biographical   History  of  Philosophy," 
New  York,  1883,  vol.  ii,  pp.  618-629. 

Falckenberg's  "  Geschichte  der  Neueren  Philosophic," 
Leipzig,  1886,  pp.  180-82. 

J.  E.  Erdmann,  'History  of  Philosophy,"  ed.  by  W.  S. 
Hough,  London  and  New  York,  1890,  pp.  271-4. 


RELATION  OF  REID'S  PHILOSOPHY   TO 
ITS  PHILOSOPHICAL  ANTECEDENTS. 


REID'S  philosophy,  like  every  other  system  of  philos- 
ophy, cannot  be  thoroughly  understood  without  taking 
into  consideration  its  relation  to  preceding  philosophic 
thought.  It  was  one  of  twQjnovements  in  the  world  of 
philosophy  awakengd  by  the  scepticism  of  Hume — the 
Philosophy  of  Common  Sense,  and  the  Critical  Philos- 
ophy of  Kant.  Reid  had  been  a  disciple  of  Berkeley, 
virtually  accepting  the  iSealismTof  that  acute  thinker. 
But  when  he  saw  what  he  thought  to  be  the  logical  out- 
come of  Berkeley's  philosophy,  as  manifested  in  the 
scepticism  of  Hume,  he  was  somewhat  alarmed,  and  be- 
gan to  suspect  the  validity  of  ' '  the  principles  commonly 
received  with  regard  to  the  human  understanding."* 
After  careful  examination,  he  came  to  the  conclusion 
that  Hume's  scepticism  was  the  legitimate  outcome  of 
the  "theory  of  ideas,"  i.  e.,  the  theory  of  perception, 
upon  which  it  was  founded.  In  his  letter,  dedicating 
the  "  Inquiry  "  to  James,  Earl  of  Findlaterand  Seafield, 
he  says:  "For  my  own  satisfaction,  I  entered  into  a 
serious  examination  of  the  principles  upon  which  this 
Sceptical  system  is  built;  and  was  not  a  little  surprised  to 
Ifind  that  it  leans  with  its  whole  weight  upon  a  hypothesis 
Which  is  ancient  indeed,  and  hath  been  very  generally 
*  "Works,"  vol.  i,  I.  P.,  p.  283. 


12  RELATION  OF    REID'S  PHILOSOPHY 

received  by  philosophers,  but  of  which  I  could  find  no 
solid  proof.  The  hypothesis  I  mean  is,  that  nothing  is 
perceived  but  what  is  in  the  mind  which  perceives  it. 
That  we  do  not  really  perceive  things  that  are  external, 
but  only  certain  images  and  pictures  of  them  imprinted 
upon  the  mind,  ^vEicITare  csffistirimpremons  and  ideas. "  * 
This  theory  he  ascribed  to  all  preceding  philosophy — 
both  ancient  and  modern.  In  regard  toHDescartes, 
Malebranche,  Locke,  Berkeley,  and  Hume,  he  says: 
"The  system  of  all  these  authors  is  the  same,  and  leads 
to  scepticism. "  ' '  Descartes  no  sooner  began  to  dig  in 
this  mine,  than  scepticism  was  ready  to  brea^k  in  upon 
him.  He  did  what  he  could  to  shut  it  out  Malebranche 
and  Locke,  who  dug  deeper,  found  the  difficulty  of 
keeping  out  this  enemy  still  to  increase:  but  they  labored 
honestly  in  the  design.  Then  Berkeley,  who  carried  on 
the  work,  despairing  of  securing  all,  bethought  himself 
of  an  expedient: — By  giving  up  the  material  world,  which 
he  thought  might  be  spared  without  loss,  and  even  with 
advantage,  he  hoped,  by  an  impregnable  partition,  to 
secure  the  world  of  spirits.  But,  alas  !  the  '  Treatise  of 
Human  Nature '  wantonly  sapped  the  foundation  of  this 
partition,  and  drowned  all  in  one  universal  deluge. "  f  It 
was  the  sceptical  outcome  of  this  "theory  of  ideas  "  which 
awakened  Reid  from  his  serene  repose  in  authority,  just 
as  later  it  awakened  Kant  from  his  dogmatic  slumber, 
and  he  resolved  to  make  a  new  inquiry  into  "this  sub- 
ject," independent  of  authority;  for,  said  he:  "I  thought 
it  unreasonable,  upon  the  authority  of  philosophers,  to 
admit  a  hypothesis  which,  in  my  opinion,  overturns  all 
*  «  Works,"  Inq.,  p.  96.  f  Ibid.,  p.  103. 


TO  ITS  PHILOSOPHICAL  ANTECEDENTS.  13 

philosophy,  all  religion  and  virtue,  and  all  common 
sense  —  and,  finding  that  all  systems  concerning  the  human 
understanding  which  I  was  acquainted  with,  were  built 
upon  this  hypothesis,  I  resolved  to  inquire  into  this  sub- 
ject anew,  without  regard  to  any  hypothesis.  "  *  Since, 
then,  the  special  task  of  Reid  was  an  examination  of  the 
'  '  theory  of  ideas,  "  it  may  be  well  for  a  thorough  ap- 
preciation of  his  task,  to  briefly  survey  the  development 
of  modern  philosophy  from  Descartes  to  Reid,  with  spe- 
cial reference  to  the  "  theory  of  ideas." 

The  scepticism  into  which  modern  philosophy  had 
issued,  prior  to  Reid,  seems  to  have  been  the  result  of 
its  peculiar  subjective  tendency.  This  tendency  char- 
acterized it  from  the  beginning.  Descartes'  sceptical 
method  forced  him  back  upon  the  authorityoTconScious- 
ness.  His^slaitmg^poinTln  philosophy  was  universal 
doubt.  f  But  this  very  fact  of  doubt  led  him  to  the  rec- 
ognition of  a  fact  that  had  to  be  accepted  —  his  own 
existence;  Because,  he  reasoned,  though  I  doubt  every- 
thing, doubt,  at  least,  remains.  Doubt,  however,  is  a 
form  of  thought.  Hence  the  form  ula?  —  cogild^  ergo 


Now7~it  is  possible  to  think  myself  devoid  of 
everything  but  thought;  hence  I  must  conclude  that  I 
am  a  being,  the  very  essence  of  which  is  thought.  § 
Thus  we  arrive  at  a  knowledge  of  mind.  But  what  of 
our  knowledge  of  an  external  world  ?  He  inferred  from 
the  existence  of  clear  and  distinct  ideas  of  things  in  the 

*«  Works,"  Inq.,  p.  96. 
f  "  First  Meditation." 
J"  Second  Meditation." 
§  Ibid. 


14  RELATION  OF    REID'S  PHILOSOPHY 

r  mind,  the  objective  reality  of  things  which  occasioned 
them — that  these  ideas  were  images  or  copies  of  things 
existing  without  the  mind.*  In  short,  his  theory  of 
perception  is  representative  perception.  However,  this 
vicarious  or  representative  character  ~of  ideas  is  only  in- 
ferential with  Descartes.  He  falls  back  upon  the  vera- 
city of  God,  (whose  existence  and  veracity  are  known  to 
us  through  our  innate  idea  of  God  f )  for  the  trustworthiness 
of  our  knowledge  of  the  external  world.  J  We  see,  then, 
in  both  the  sceptical  method  of  Descartes,  and  also  in  his 
theory  of  representative  perception  the  subjective  tend- 
ency referred  to  above. 

Turning  to  Mai ebranche  we  find  in  his  teaching,  also,  this 
subjective  trend  manifested.  He  says,  material  things 
are  known  to  us  only  under  the  forms  of  ideas.  §  As  to 
the  origin  of  these  ideas,  we  are  informed  that  they  are 
not  originated  by  the  mind  from  itself— because  of  its 
inability.  ||  Neither  are  they  given  to  us  by  things  them- 
selves, fl  How,  then,  do  we  come  into  possession  of 
them  ?  Malebranche  answers  :  through  the  mind's  union 
with  God,  who  possesses  within  Himself  ideas  repre- 
senting all  things  created  by  Him.  God,  by  His  pres- 
ence, is  united  to  the  finite  mind — He  being  the  ' '  place 
of  spirits  "  just  as  "  space  is  the  place  of  bodies."  This 
union  makes  it  possible  for  the  mind  to  see  in  God  that 

*  "  Sixth  Meditation." 

f  "  Third  and  Fourth  Meditations.' 

J  "Sixth  Meditation." 

§  "  Dela  Recherche  de  la  Verite,"  Ivr.  iii,  pt.  ii,  ch.  I. 

||  Ibid.,  ch.  3. 

11  Ibid.,  Ch.  2. 


TO  ITS  PHILOSOPHICAL    ANTECEDENTS.  15 

which  represents  things,  viz.,  ideas.*     It  is  thus  that 
f '  we  see  all  things  in  God." 

In  the  philosophy  of  Locke  we  find  the  same  element 
of  subjectivity.  He  wrote  hisTamous  ' l  EsSayrnrHuman 
Understanding  "  with  the  purpose  of  explaining  the  or- 
igin, certainty  and  extent  of  knowledge.  After  explain- 
ing away  all  innate  ideas,  f~Xocke~  endeavored  to  show 
how  we  come  into  possession  of  ideas.  He  assumes 
that  the  mind  in  its  original  condition  is  like  a  blank 
sheet  of  paper,  or  a  tabula  rasa.  J  Whence,  then,  come 
its  ideas  ?  The  source  of  ideas  is  experience — sensation  and 
reflection.  §  Having  thus  given  the  source  of  our  ideas, 
he~clivides  them  into  two  kinds,  simple  and  complex. 
A  simple  idea  contains  in  it  nothing  but  a  uniform  ap- 
pearance or  conception  in  the  mind,  and  is  not  distin- 
guishable into  different  ideas.  These  constitute  the  ma- 
terial of  all  knowledge.  Complex  ideas  are  formed  by 
the  mind  by  combining  and  uniting  simple  ideas.  || 
Locke  then  proceeds  to  make  another  distinction  be- 
tween our  ideas,  by  pointing  out  the  objective  character 
of  some,  and  the  subjective  character  of  others.  He, 
of  course,  assumes  the  existence  of  an  external  world  of 
corrjoreaTbodies.  Now,  that  which  in  a  body  occasions 
an  idea  in  the  mind,  he  calls  a  quality.  There  are 
some  qualities  in  bodies  which  cause  ideas  in  the  mind 
which  are  exact  likenesses  or  resemblances  of  these 
qualities.  Thejdea  in  the  mind  is  a  copy  of  the  quali- 
ty in  the  body.  These  qualities  are  called  primary 

*  "  De  la  Recherche  de  la  Verite,"  Ivr.  iii.  pt.  ii,  ch.  3. 
f  "  Essay,"  bk.  i,  chs.  2,  3,  4-        t  "  Essay,"  bk.  ii,  ch.  I. 
§  Ibid.,  bk.  ii.,  ch.  i.  H  Ibid.,  ch.  2. 

15 


l6  RELATION  OF  REID'S  PHILOSOPHY 

or  original  qualities  of  matter,  viz.,  extension,  solid- 
ity, figure,  motion,  number,  etc.  But  there  are  other 
ideas  in  the  mind  which  have  no  resemblance  to  the 
qualities  in  the  bodies  which  cause  them.  To  this  class 
belong  most  of  the  ideas  of  sensation,  viz.,  colors, 
sounds,  tastes,  smells,  etc.  These  do  not  resemble  their 
causes.  The  qualities  which  cause  such  ideas  in  us  are 
the  secondary  qualities  of  bodies.* 

Locke  then  proceeds  to  the  explanation  of  the  idea  of 
substance,  and  it  is  important  to  note  his  remarks  on 
this  point,  because  of  the  positions  taken  by  Berkeley 
and  Hume  afterward.  This  idea,  according  to  Locke, 
is  not  derived  from  sensation  and  reflection,  as  simple 
ideas  are  derived.  Its  origin  is  as  follows:  We  frequent- 
ly recognize  a  certain  combination  of  simple  ideas,  and 
we  cannot  conceive  them  as  self-subsisting,  so  we  are 
wont  to  provide  a  substratum  for  them  as  a  ground  of 
subsistence,  and  as  a  cause  of  their  existence,  which  we 
call  substance.  However,  although  substance  is  an 
abstract  idea,  he  believed  in  its  objective  reality,  f 

After  this  consideration  of  the  sources  and  kinds  of 
ideas  the  mind  has,  we  are  prepared  to  hear  Locke's 
conception  of  knowledge.  Knowledge  is  simply  "con- 
versant about  our  ideas."  It  is,  "nothing  but  the 
perception  of  the  connection  and  agreement  or  'dis- 
agreement' and  repugnancy  of  any  of  our  ideas." 
Things  are  not  known  immediately  by  the  mind,  but 
through  the  intervention  of  ideas.  How  far,  then,  is 
knowledge  real  ?  Only  "  so  far  as  there  is  a  conformity 
between  our  ideas  and  the  reality  of  things."  But  what 

*  "  Essay,"  bk.  ii,  ch.  8.  t.Ibid-»  bk-  "»  ch-  23» 


TO  ITS  PHILOSOPHICAL    ANTECEDENTS.  17 

shall  be  our  criterion  in  determining  this  conformity  ? 
As  Locke  himself  asks:  * '  How  shall  the  mind.when  it 
perceives  nothing  but  its  own  ideas,  know,  that  they 
agree  with  things  themselves  ?  "  He  answers  this  ques- 
tion by  telling  us  that  there  are  two  kinds  of  ideas  of 
which  we  may  have  assurance  of  their  agreement  with 
things.  First,  we  have  simple  ideas,  which  are  affections 
of  the  mind  produced  by  external  things,  ' '  operating  on 
the  mind  in  a  natural  way."  Hence  these  ideas  cannot 
be  fictions,  but,  being  produced  in  this  way,  they  "carry 
with  them  all  the  conformity  which  is  intended  or 
which  our  state  requires."  The  second  kind  of  ideas  to 
which  he  refers  in  this  connection,  is  complex  ideas. 
These  being  formed  by  the  mind  itself,  and  not,  with 
the  exception  of  the  ideas  of  substances,  being  intended 
to  represent  anything  external,  cannot  mislead  us.* 

We  see,  then,  in  what  Locke  says  in  regard  to  know- 
ledge, a  recognition  of  its  subjectivity.  He  admits  that 
the  mind  does  not  have  an  immediate  knowledge  of 
things.  It  only  knows  them  ' '  by  the  intervention  of 
ideas. "  He  gives  no  other  than  a  practical  reason  for 
the~correspondence  of  ideas  and  things.  In  this  recogni- 
tion of  the  subjective  character  of  our  knowledge  he  cer- 
tainly anticipated  Berkeley,  as  Reid  suggests.  He  even 
anticipated  Hume,  and  his  taking  refuge  in  a  practical 
reason  was  doubtless  more  for  the  purpose  of  avoiding 
scepticism  than  idealism.  Even  for  the  assumption  of 
the  existence  of  an  external  world  of  corporeal  substances, 
involved  in  his  theory  of  perception,  he  really  gives  us  no 
warrant  of  a  speculative  character.  This,  too,  he  ulti- 

*  «  Essay,"  bk.  iv,  chs.  i,  4. 


1 8  RELATION   OF   REID'S   PHILOSOPHY 

mately  rests  on  practical  grounds;  apparently,  also,  for 
the  purpose  of  escaping  scepticism. 

It  was  this  subjectivity  of  knowledge  as  involved  in 
Locke's  "  theory  of  ideas,"  and  the  idealism  and  scepti- 
cism which  were  ultimately  developed  from  it,  which  at- 
tracted Reid's  attention,  and  impelled  him  to  examine 
this  theory,  hoping  to  be  instrumental  in  its  overthrow, 
and  to  establish  knowledge  on  a  firm  foundation.  We 
must,  then,  trace  this  subjective  tendency  as  manifested 
in  the  philosophy  of  Berkeley,  and  then  in  the  scepti- 
cism of  Hume,  which  awakened  the  reactionary  philos- 
ophy of  Reid. 

Berkeley's  problem,  as  Prof.  Fraser  suggests,  was  an 
inquiry  into  the  real  meaning  of  substance  and  cause  as 
external.  In  answering  the  first  part  of  the  question, 
the  real  meaning  of  material  substance,  he  endeavored 
to  show  that  the  doctrine  of  substance  as  advocated  by 
the  philosophers,  involved  a  contradiction.  He  claimed 
that  the  objects  of  knowledge  are  ideas,  which  ideas,  of 
course,  exist  in  the  mind.  Knowledge  is  concerned 
only  with  ideas.  Now,  when  we  ask  what  is  meant  by 
the  existence  of  sensible  things,  it  is  evident  ' '  that  their 
esse  is  percipi. "  All  that  really  is  meant  by  the  exist- 
ence of  a  thing  is  that  it  is  seen,  touched,  etc.,— in  short, 
that  it  is  perceived.  To  speak  of  something  existing 
independent  of  a  mind  perceiving  it  is  unintelligible  and 
impossible.  So-called  things  are  objects  perceived  by 
sense,  "  and  what  do  we  perceive  besides  our  own  ideas 
or  sensations  ?  and  is  it  not  plainly  repugnant  that  any 
one  of  these,  or  any  combination  of  them,  should  exist 
unperceived  ?  "  The  being  of  things,  then,  consists  in 
their  being  perceived.  Ideas  cannot  be  images  of  sub- 


TO  ITS   PHILOSOPHICAL    ANTECEDENTS.  19 

stantial  things,  because  an  idea  can  only  be  like  an  idea, 
and  things  to  be  perceived  must  be  ideas,  and,  if  not, 
there  is  no  sense  in  saying  an  idea  is  like  something  of 
which  we  can  know  nothing.* 

Berkeley  then  discusses  the  subject  of  primary  and 
secondary  qualities,  in  which  discussion  he  apparently 
had  Locke  in  mind.  He  objects  to  the  distinction 
made  by  Locke,  affirming  our  knowledge  of  primary 
qualities  to  be  just  as  subjective  as  our  knowledge  of 
secondary  qualities;  extension,  solidity,  figure,  etc.,  are 
ideas  in  the  mind  just  as  colors,  odors,  etc.,  are  ideas; 
and,  as  ideas  can  only  resemble  ideas,  and,  as  they  exist 
only  in  the  mind,  extension,  figure,  etc. ,  cannot  exist  in 
an  unthinking  external  substance.  The  very  ' '  notion  " 
of  matter,  then,  involves  a  contradiction,  f 

But  if  there  be  no  external  material  substance — if 
there  be  no  world  of  corporeal  substances — how  are  we 
to  account  for  the  existence  of  our  ideas  ?  They  must 
have  a  cause.  This  brings  us  to  the  consideration  of  the 
second  part  of  Berkeley's  question,  the  nature  of  the 
originating  cause.  This  cause,  he  says,  cannot  be  an 
idea,  for  all  ideas  are  "visibly  inactive."  "There  is 
nothing  of  power  or  agency  in  them, "  and  hence  an 
idea  cannot  be  a  cause.  In  the  second  place,  the  cause 
cannot  be  a  material  substance,  for  we  have  seen  there  is 
no  such  thing.  What,  then,  is  the  cause  ?  The  cause 
of  the  ideas  must  be  an  "incorporeal  active  substance 
or  spirit."  But  it  is  not  my  spirit  which  originates  them, 
because  the  ideas  of  sense  are  not  originated  by  me — 

*  "  Principles,"  §§  4,  6,  8,  10.  f  Ibid->  §  15- 


20  RELATION  OF  REID'S   PHILOSOPHY. 

they  are  not  produced  by  my  will.  The  Will  or  Spirit 
which  does  originate  them  Berkeley  infers  to  be  God.* 

In  our  knowledge  of  spirit  we  seem  to  be  conversant 
with  something  more  than  ideas.  He  tells  us  we  have 
no  idea  of  a  spirit  and  can  have  none.  However,  he 
says,  we  have  a  "  notion"  of  spirit.  We  have  also  a 
"notion"  of  other  spirits  and  of  relations.  "We  com- 
prehend our  own  existence  by  inward  feeling  or  Reflection, 
and  that  of  other  spirits  by  Reason  (inference).  We  may 
be  said  to  have  some  knowledge  or  notion  of  our  own 
minds,  of  spirits  and  active  beings,  whereof  in  a  strict 
sense  we  have  not  ideas.  In  like  manner  we  know 
and  have  a  notion  of  relations  between  things  or  ideas, 
which  relations  are  distinct  from  the  ideas  or  things  re- 
lated, inasmuch  as  the  latter  may  be  perceived  by  us 
without  our  perceiving  the  former,  "f  The  preceding 
quotation  is  important  as  showing  Berkeley's  deviation 
from  the  position  taken  in  the  beginning  of  the  ' '  Princi- 
ples," where  he  affirmed  ideas  to  constitute  the  objects 
of  our  knowledge  (see  §  i).  Here  he  recognizes  another 
object  of  knowledge  in  ' '  notions. "  Reid  suggests  that 
Berkeley  took  refuge  in  the  ' '  notion  "  because  of  an  aver- 
sion to  scepticism.  J 

Thus  we  see  that  Berkeley,  beginning  with  Locke's 
doctrine  of  ideas  as  the  only  objects  of  knowledge, 
carried  it  so  far  as  to  reject  his  arbitrary  assumption 
as  to  the  objective  character  of  certain  ideas,  existing 
as  qualities  of  a  substratum  called  substance,  which 
substratum  is  also  an  unwarrantable  assumption,  thus 

*  "  Principles,"  §§  25,  26,  29.         f  Ibid.,  §  89,  cf.  also  §  27. 
|  "Works,"  Inq.,  p.  207. 


TO  ITS   PHILOSOPHICAL  ANTECEDENTS.  21 

resolving  the  world  of  material  things  into  a  world  of 
ideas.  In  all  of  this  the  subjectivity  heretofore  referred 
to  is  still  more  manifest  than  in  the  preceding  systems 
considered.  In  the  philosophy  of  Hume,  which  we  are 
now  to  consider,  we  shall  see  the  culmination  of  this 
subjective  tendency  in  scepticism. 

In  the  "Treatise  on  Human  Nature"  Hume  argues  as 
follows : — 

"  All  perceptions  of  the  human  mind  resolve  them- 
selves into  two  distinct  kinds,  which  I  shall  call  impres- 
sions and  ideas."  By  impressions,  he  means,  "sen- 
sations, passions,  and  emotions."  By  ideas,  he  means, 
"the  faint  images  of  these  in  thinking  and  reasoning." 
Ideas,  then,  are  images  of  impressions.*  Every  simple 
impression  has  its  corresponding  idea,  and  every  simple 
idea  has  its  corresponding  impression,  and  he  holds  to 
the  general  proposition,  ' '  That  all  our  simple  ideas,  in 
their  first  appearance,  are  derivd  from  simple  impressions, 
which  are  correspondent  to  them,  and  which  they  exactly 
represent,  "f 

As  to  the  'division  of  impressions  and  ideas  Hume  said, 
that  they  could  be  divided  into  two  classes — simple  and 
complex.  Simple  impressions  and  ideas  admit  of  no 
distinction  and  are  inseparable.  Complex  ideas  are 
distinguishable  into  parts.  Complex  ideas  include  ideas 
of  substances,  modes  and  relations.  "The  idea  of  a 
substance  as  well  as  that  of  a  mode,  is  nothing  but  a 
collection  of  simple  ideas  that  are  united  by  the  imagi- 
nation, and  have  a  particular  name  assigned  them,  by 

*  •«  Treatise  on  Human  Nature,"  ed.  by  Green  and  Grose,  Lon. 
don,  1886,  vol.  I,  p.  311.  |  Ibid,,  p.  314. 


22  RELATION  OF   REID'S   PHILOSOPHY 

which  we  are  able  to  recall,  either  to  ourselves  or  others, 
that  collection."*  Since  we  have  no  simple  idea  of  sub- 
stance, derived  from  an  impression  of  sense,  Hume 
joined  with  Berkeley  in  refusing  to  affirm  the  objective 
existence  of  material  substance. 

He  then  takes  up  the  question  of  knowledge.  Here 
he  makes  quite  an  effort  to  provide  for  that  synthesis 
which  knowledge  implies.  He  finds  this  synthetic 
power  in  imagination,  with  its  principles  of  association. 
In  knowledge  the  imagination  deals  with  seven  different 
kinds  of  relations:  "Resemblance,  identity,  relations 
of  time  and  place,  proportion  in  quantity  or  number, 
degrees  in  any  quality,  contrariety,  and  causation. "  f 
These  relations  may  be  divided  into  two  classes,  the 
one  depending  upon  the  ideas  compared  :  the  other 
relations  are  "such  as  may  be  changed  without  any 
change  in  the  ideas."  Resemblance,  contrariety,  degree, 
proportion  belong  to  the  first  class.  They  arise  out  of 
the  very  nature  of  the  ideas,  and  certainty  can  only  arise 
with  these  as  objects  of  knowledge,  but  the  knowledge  is 
purely  subjective.  It  can  never  transcend  perceptions. 
Hume  says  that  in  the  other  class  of  relations  it  seems  as 
though  we  are  carried  beyond  our  perceptions,  but  in 
this  we  are  deceived.  Neither  identity,  nor  time,  nor 
space  carries  us  beyond  perceptions.!  But  how  is  it 
with  causation  ?  Here  we  seem  to  have  assurance  of 
conclusions  which  extend  beyond  the  impressions  of 
sense.  §  Hence  this  relation  must  be  carefully  examined, 
and  this  examination  on  the  part  of  Hume  constitutes 

*  "Treatise,"  pp.  312,  313,  321,  324.          f  Ibid.,  p.  372. 
J  Ibid.,  pp.  375,  sq.  §  Ibid.,  pp-376-7- 


TO    ITS    PHILOSOPHICAL    ANTECEDENTS.  23 

the  principal  merit  of  his  philosophy.  When  we  believe 
in  the  existence  of  an  object  we  have  simply  an  idea  of 
the  object — and  no  additional  idea,  and  belief  is  distin- 
guished from  incredulity  simply  in  its  superior  liveliness 
and  vigor.  The  vividness  of  an  idea  and  belief  are  one 
and  the  same.  Now,  when  an  impression  is  vivid  it  gives 
its  vividness  to  the  ideas  associated  with  it  by  resemblance, 
contiguity  or  causation.*  Now,  how  are  we  to  explain 
our  belief  in  causation  ?  This  idea  we  gain  from  ex- 
perience. Experience  presents  us  with  objects  in  con- 
stant conjunction,  and  thus  produces  in  us  "a  habit 
of  surveying  them  in  that  relation,  that  we  cannot 
without  a  sensible  violence  survey  them  in  any  oth- 
er, "f  But  whence  the  belief  of  necessary  connection 
implied  in  the  relation  of  cause  and  effect  ?  This 
may  be  accounted  for  by  a  propensity,  born  of  cus- 
tom, to  pass  from  the  impression  or  idea  of  an  object  to 
the  idea  of  the  object  which  usually  attends  it.  "  When 
any  object  is  presented  to  it,  it  immediately  conveys  to 
the  mind  a  lively  idea  of  that  object  which  is  usually 
found  to  attend  it,  and  this  determination  forms  the  ne- 
cessary connection  of  these  objects.  "J  In  brief,  we 
mean  by  causation  simply  this  :  that  when  two  objects 
have  been  constantly  conjoined  (in  experience),  the  pres- 
ence of  one  determines  the  mind  to  form  the  idea  of  the 
other,  and  this  determination  is  the  result  of  habit  or  cus- 
tom. Hence  this  relation  of  cause  and  effect,  which  at  first 
seemed  to  carry  us  beyond  impressions,  does  not  really 
do  so,  but  resolves  itself  into  a  propensity,  begotten  of 

*  "Treatise,"  pp.  394-400,  sq.  f  Ibid.,  p.  424. 

t  Ibid.,  pp.  450-68. 


24  RELATION    OF    REID'S    PHILOSOPHY 

custom,  to  pass  from  the  impression  or  idea  of  an  object 
to  the  idea  of  that  object  which  usually  attends  it.  The 
causal  relation  between  things  and  ideas  involved  in 
the  theory  of  Locke,  Hume  regarded  as  a  mere  assump- 
tion which  experience  did  not  justify.  "  The  mind,"  he 
says,  "has  never  anything  present  to  it  but  the  percep- 
tions, and  cannot  possibly  reach  the  experience  of  their 
connection  with  objects.  The  supposition  of  such  a 
connection  is,  therefore,  without  any  foundation  in  rea- 
soning." The  ultimate  realities,  then,  with  which  the 
mind  has  to  deal  are  individual,  unreferable  impressions, 
and  from  such  impressions  we  cannot  infer  the  existence 
of  external  material  objects.  Here  we  see  idealism  pure 
and  simple. 

But  he  did  not  rest  content  with  a  denial  of  the  reality  of 
an  external  world;  he  also  denied  the  reality  of  the  soul. 
"  Since  all  our  perceptions  are  different  from  each  other, 
and  from  everything  else  in  the  universe,  they  are  also  dis- 
tinct and  separable,  and  may  be  considered  as  separately 
existent,  and  may  exist  separately,  and  have  no  need  of 
anything  else  to  support  their  existence."  *  Hence  there 
is  no  necessity  of  a  self  as  a  substratum  or  subject  of  our 
perceptions.  Proceeding  upon  his  original  thesis,  that 
the  perceptions  of  the  mind  are  resolvable  into  impres- 
sions and  ideas — ideas  being  mere  images  of  impressions 
— he  says  :  "  If  any  impression  gives  rise  to  the  idea  of 
self,  that  impression  must  continue  invariably  the  same, 
through  the  whole  course  of  our  lives  ;  since  self  is  sup- 
posed to  exist  after  that  manner.  But  there  is  no  impres- 

*  "Treatise,"  p.  5r8. 


TO    ITS    PHILOSOPHICAL    ANTECEDENTS.  25 

sion  constant  and  invariable.  Pain  and  pleasure,  grief 
and  joy,  passions  and  sensations  succeed  each  other, 
and  never  all  exist  at  the  same  time.  It  cannot,  there- 
fore, be  from  any  of  these  impressions,  or  from  any 
other,  that  the  idea  of  self  is  derived,  and  consequently 
there  is  no  such  idea"  *  Hume  thinks  we  have  no  more 
an  idea  of  a  thinking  substance  as  the  support  of  per- 
ceptions than  we  have  of  an  external  substance  as  the 
support  of  qualities,  and  Berkeley  in  rejecting  the  one 
ought  to  have  rejected  the  other,  f 

To  make  his  scepticism  complete,  Hume  impeaches 
the  veracity  of  reason  :  (i)  Because  it  leads  to  con- 
clusions different  from  those  of  the  senses  ;  (2)  Because 
it  is  so  frequently  found  to  be  fallible.  (3)  Because  each 
judgment  must  be  tested  by  other  judgments  "contain- 
ing uncertainty,"  and  these  in  turn  by  other  judgments 
containing  uncertainty,  and  so  Qnadmfinitum.  Nihilistic 
scepticism  is  the  fruit  of  Hume's  endeavors.  J 

Thus,  in  our  brief  historical  survey  of  modern  philos- 
ophy down-  to  Hume,  we  find  it  culminating  in  scepti- 
cism. The  subjectivity  which  characterizes  it  from  the 
beginning  peculiarly  paves  the  way  toward  the  conclu- 
sion. It  was  against  this  scepticism  thatReid  recoiled. 
Repugnant  as  it  was  to  him,  and,  as  before  stated,  be- 
lieving it  to  be  "  inlaid  "  in  all  modern  philosophy,  and 
traceable  to  the  theory  of  perception  which  he  believed 
to  be  common  to  these  systems,  §  he  determined  to 
make  a  new  inquiry  into  the  subject,  with  the  pur- 


*  "Treatise,"  p.  533.  f  Ibid.,  pp.  517-18. 


"reatse,     p.  533.  f         .,  pp.  517-1. 

Ibid.,  p.  472,  sg.  §  "  Works,"  Inq.,  pp.  96,  103,  106. 


26  RELATION    OF    REID'S    PHILOSOPHY 

pose  of  refuting  this  theory  of  perception,  and  plac- 
ing philosophy  upon  a  new  basis,  by  substituting  a 
new  theory  of  perception,  and  a  new  philosophical 
organon  in  the  principle  of  common  sense. 

In  inquiring  anew  into  this  subject,  Reid  adopted  a 
particular  method.     The  "  Inquiry"  especially  bears  the 
marks  of  its  age.     Like   other  systems  of  philosophy, 
it  is  affected  by  the  "  Zeit-Geist."     It  is  not  often,  if  ever, 
that  we  have  a  purely  closet  philosophy — a   philosophy 
produced  absolutely  independent   of  the   spirit   of  the 
age.     Consciously  or  unconsciously   speculation   is   af- 
fected by  the  subtle  influences   of  the   intellectual    and 
moral  atmosphere  in  which  it   is    brought    forth.     This 
influence  of  the  spirit  of  the  age  upon  Reid's  philosophy 
may  be  seen  in  the  method  which  he  adopts — the  exper- 
imental or  inductive  method.     The  results  of  an    appli- 
cation of  this  method  in  the  study  of  physical    phenom- 
ena, by  such  men  as  Newton,  were   wonderful.     Reid, 
who  was  an  earnest  student  of  physics,  was  greatly   im- 
pressed by  the  validity  and  fruitfulness  of  this    method, 
and  he  came  to  the  conclusion  that  it  was  the  only 
method  which  should  be  employed  in  the  investigation  of 
the  phenomena  of  the  mind,  and  determined  to   apply 
it.     All  through  the  "Inquiry"  the  steadfastness  of  his 
purpose  is   manifest.      Dugald   Stewart   truly   remarks, 
that  "the  influence  of  the  general  view   opened   in   the 
'  Novum  Organon'  may  be  traced  in  almost  every  page 
of  his  writings:  and,  indeed,  the  circumstance  by  which 
these  are  so  strongly  and  characteristically  distinguished, 
is  that  they  exhibit  the  first  systematical  attempt  to   ex- 
emplify in  the  study  of  human  nature   the  same  plan  of 


TO    ITS    PHILOSOPHICAL   ANTECEDENTS.  27 

investigation  which  conducted  Newton  to  the  properties 
of  light  and  to  the  law  of  gravitation. "  * 

Having  thus  stated  the  aim  and  method  of  Reid's 
philosophy,  let  us  proceed  to  an  exposition  of  the  same. 
And,  first,  let  us  consider  the  theory  of  perception,  which 
he  urged  in  opposition  to  the  "  theory  of  ideas." 

His  theory  of  perception  has  both  negative  and  positive 
aspects.  In  its  negative  aspect,  it  is  a  denial  of  (i)  the 
particular  form  of  perception  which  Reid  ascribed  to 
all  preceding  philosophy.  This  particular  form  Reid 
conceived  to  be,  as  Hamilton  suggests,  that  the  object 
before  the  mind  in  perception  is  ' '  always  a  tertium  guid  I 
numerically  different  both  from  the  object  existing  and  "  | 
from  the  subject  knowing. "  f  This  is  the  theory  which 
Reid  felt  called  upon  to  den^ — the  calling  into  question 
of  which  he  deemed  to  be  the  special  merit  of  his  own 
philosophy.J  (2)  In  its  negative  aspect,  Reid's  theory 
of  perception  is  a  denial  that  we  attain  our  knowledge 
of  external  objects  by  an  act  of  reasoning. 

In  denying  the  theory  of  ideas  his  argument  runs  as 
follows:  § 

i.  The  theory  is  in  direct  opposition  to  the  universal 
sense  of  men  uninstructed  in  philosophy.  When  a  plain 
man  sees  the  sun  and  moon  he  does  not  doubt  that  there 
are  objects  far  distant  from  himself,  and  not  merely  ideas 
in  his  mind.  If  he  asks  whether  there  are  no  substantial 
beings  called  sun  and  moon,  the  answer  which  he  will 


*  "Collected  Works,"  vol.  x,  p.  259. 

t  Works,  Inq.,  Note,  p.  106. 

J  Ibid.,  p.  88. 

§  Cf.  "  Works,"  Inq.,  pp.  201-1 1  and  especially  I.  P.,  pp.  298-309. 


28  RELATION    OF    REID'S    PHILOSOPHY 

get  from  the  philosophers   will  differ.     Locke  and  his 

^""7 

predecessors  will  answer,  that  there  are  such  beings,  but 
they  never  appear  to  us  in  person,  but  only  b^_ideas — 
which  are  their  representatives  in  our  minds,  and  all  we 
know  of  them  must  be  gained  from  these  ideas.  Berke- 
ley and  Hume  would  say,  that  there  are  no  such  sub- 
stantial beings.  That  is  simply  a  prejudice  of  the 
vulgar.  Berkeley  would  say  that  nothing  exists  but  ideas 
and  minds,  and  these  things  are  simply  ideas  in  our 
minds.  Hume  would  say,  only  ideas  exist,  and  the 
mind  is  simply  a  series  of  ideas  bound  together  by  a  few 
relations!  To  the  plain  man  tKis  must,  of  course,  be  op- 
posed to  "the  dictates  of  common  understanding." 

2.  Those  who  advocate  the  "theory  of  ideas"  have, 
as  a  rule,  assumed  the  existence  of  the  ideas,  and  have 
regarded  their  existence  as   unquestionable.     The  few 
arguments  which  they  have  incidentally  offered  in  their 
behalf  have  been  "  too  weak  to  support  the  conclusion." 
Locke,  for  example,  says  we  are  conscious  of  such  ideas. 
But,  says  Reid,  we  are  not  conscious  of  them.     All  we 
are  conscious  of,  are  the  operations  of  the  mind,  such  as 
perceiving,  remembering,  etc.,  and  not  of  the  objects  of 
such  operations.   And  thus  he  quotes  others,  endeavoring 
to  show  the  assumptive  character  of  their  positions,  and 
the  weakness  of  their  "incidental  arguments." 

3.  Although  there  is  a  unanimous  agreement  among 
philosophers  on  the  subject  of  the  existence  of  ideas, 
there  seems  to  be  a  pronounced  disagreement  among 
them  with  respect  to  everything  else  concerning  the  ideas. 
This  ought  not  to  be,  if  they  are  a  reality,  for  of  all  things 
they  ought  to  be  most  easily  accessible  to  knowledge. 
Some  hold  that  they  are  self-existent;  others,  that  they 


TO    ITS    PHILOSOPHICAL    ANTECEDENTS.  IQ 

exist  in  the  Divine  mind.  Some  hold  that  they  exist  in 
our  minds;  others,  that  they  exist  in  the  brain  or 
sensorium.  Some  hold  that  they  are  innate,  or,  at  least, 
a  part  of  them;  others,  that  they  are  all  adventitious. 
Some,  that  they  are  gained  through  the  senses;  others, 
that  they  are  derived  from  sensation  and  reflection.  As 
to  how  they  arise,  some  think  the  mind  originates  them; 
others,  that  they  are  occasioned  by  external  causes:  still 
others,  that  they  are  produced  by  God  acting  upon  the 
mind.  And  so  on,  in  regard  to  other  features  of  the 
ideas  there  is  this  wide  disagreement.  This,  as  has  been 
suggested,  ought  not  to  be,  if  ideas  really  exist,  for  they 
ought  to  be  very  accessible  to  knowledge. 

4.  Ideas  do  not  improve  our  knowledge  of  the  various 
operations  of  the  mind.     They  .were,  doubtless,  brought 
forward  for  this  purpose.  ' '  This  power  of  perceiving  ideas 
is  just  as  inexplicable  as  any  of  the  powers  explained 
by  it." 

5.  The  consequences  of  this  theory  are  such  as  to  pre- 
judice every  man  against  it  who  has  a  due  regard  for  the 
common  sense  of  mankind.     Aside  from  the  peculiarities 
and  absurdities  which  flow   from  the  theory  as  seen  in 
ancient  philosophy,  we  see  in   modern  philosophy   con- 
sequences  which    are    enough   to   prejudice   mankind 
against  it.     It  has  led  to  the  attempts  of  trying  to  prove 
the  existence  of  material  things.     And  who  does  not  see 
that  philosophy  must  make  a  very  ridiculous  figure  in 
the  eyes  of  sensible  men  while  it  is  employed  in  muster- 
ing up  metaphysical  arguments  to  prove  that  there  is  a 
sun  and  a  moon,   an  earth   and  a  sea  ?      It  has  led  to 
such  paradoxes  as,  "that  the  secondary  qualities  of  body 
are  not  qualities  of  body  at  all,   but  sensations  of  the 


$O  RELATION    OF    REID*S    PHILOSOPHY 

mind:  That  the  primary  qualities  of  body  are  resem- 
blances of  our  sensations:  That  we  have  no  notion  of 
duration,  but  from  the  succession  of  ideas  in  our  minds: 
That  personal  identity  consists  in  consciousness;  so  that 
the  same  individual  thinking  being  may  make  two  or 
three  different  persons,  and  several  different  thinking  be- 
ings make  one  person:  That  judgment  is  nothing  but  a 
perception  of  the  agreement  or  disagreement  of  our  ideas." 
But  these  consequences  are  tolerable  when  brought  into 
comparison  with  those  which  we  find  in  Berkeley  and 
Hume.  Here  we  have  the  negation  of  the  world  of  mat- 
ter and  the  world  of  mind,  and  nothing  is  left  us  but 
ideas.  A  general  scepticism  is  the  result.  These  are  the 
"noble  fruits"  which  this  "theory  of  ideas  "  has  brought 
forth.  Such  consequences,  so  startling  to  common 
sense,  must  cause  a  reaction  against  the  theory. 

In  the  second  place,  Reid  denies  that  we  attain  to  a 
knowledge  of  external  objects  by  an  act  of  reasoning. 
He  depends  mainly  upon  the  strength  of  his  own  theory 
of  perception  for  an  overthrowal  of  this  doctrine. 

Having  thus  considered  the  negative  aspects  of  Reid's 
theory  of  perception  let  us  proceed  to  a  consideration  of 
its  positive  aspects. 

The  following  are  the  main  features  of  his  theory: 

I.   Sensation. 

1.  A  sensation  is  a  simple,  inexplicable  affection  of 
the  mind.      "It  appears  to  be  a  simple  and  original  af- 
fection or  feeling  of  the   mind,  altogether  inexplicable 
and  unaccountable."  * 

2.  Sensations  exist  onlyji^  f^p  miqrl      They  do  not 


Works,"  Inq.,  p.  105. 


TO    ITS    PHILOSOPHICAL    ANTECEDENTS.  31 

exist  in  material  things — not  even  in  our  own  bodies. 
"The  sensations  of  touch,  of  seeing,  and  hearing,  are  all 
in  the  mind,  and  can  have  no  existence  but  when  they 
are  perceived."  * 

3.  Sensations  are  antecedent  to  perceptions.  The 
"sensation  is  followed  by  the  perception  of  the  ob- 
ject."t 

//   Perception. 

i.  Perception  defined.  Sensation  naturally  suggests 
a  ' '  notion  "  or  u  conception  "  of,  together  with  a  be- 
lief  in  the  existence  of.  an  object  This  is  perception. 
' '  But  I  think  it  appears,  from  what  hath  been  said,  that 
there  are  natural  suggestions:  particularly  that  sensation 
suggests  the  notion  of  present  existence  and  the  belief 
that  what  we  perceive  or  feel  does  now  exist,  .  .  .  and 
that  our  sensations  and  thoughts  do  also  suggest  the 
notion  of  a  mind,  and  the  belief  of  its  existence,  and  of 
its  relation  to  our  thoughts.  .  .  .  And  in  like  manner 
.  .  .  certain  sensations  of  touch,  by  the  constitution  of 
our  nature,  suggest  to  us  extension,  solidity  and  mo- 
tion, "f  In  the  "Intellectual  Powers,"  we  find  Reid 
essentially  agreeing  with  his  definition  of  perception 
given  in  the  "Inquiry."  He  says:  "If,  therefore,  we 
attend  to  that  act  of  our  mind  which  we  call  the  perception 
of  an  external  object  of  -sense,  we  shall  find  in  it  these 
three  things: — First,  Some  conception  or  notion  of  the 
object  perceived  ;  Secondly,  a  strong  and  irresistible 
conviction  and  a  belief  of  its  present  existence;  and 

*  "Works,"  Inq.,  pp.  159,  105,  187;  I.  P.,  pp.  229,  310. 
f  Ibid.,  pp.  186,  187;  I.  P.,  p.  320. 
J  Ibid.,  Inq.,  p.  in. 


32  RELATION    OF    REID'S    PHILOSOPHY 

Thirdly,  that  this  conviction  and  belief  are  immediate, 
and  not  the  effect  of  reasoning."  In  other  words: 
Sensations  are  attended  by  certain  original  "sugges- 
tions "  and  beliefs,  and  this  constitutes  perception. 

2.  Perception  illustrated.  This  theory  of  perception 
will  be  more  intelligible  to  us  if  we  examine  Reid's 
doctrine  of  "suggestion  "  as  we  find  it  illustrated  in  his 
treatment  of  the  so-called  secondary  and  primary  quali- 
ties of  body.  Reid  agreed  with  Locke  in  regard  to  the 
essential  distinction  between  the  secondary  and  primary 
qualities,  which  Berkeley  and  Hume  had  endeavored  to 
remove.*  ~The  two  points  of  distinction  to  which  he 
directs  attention,  are:  (i)  The  ease  with  which  we 
distinguish  between  the  sensation  and  its  external  corre- 
late in  the  case  of  secondary  qualities  as  compared  with 
primary  qualities.  (2)  The  sensations  in  the  case  of 
secondary  qualities  only  suggest  a  power  or  quality  of 
the  object  as  a  cause;  whereas,  in  the  case  of  the  pri- 
mary qualities,  the  sensation  also  suggests  the  nature  of 
the  cause.  Now,  in  the  treatment  of  the  secondary  and 
primary  qualities,  as  above  stated,  we  may  see  Reid's 
theory  of  perception,  as  sensation  attended  by  original 
suggestions  and  beliefs,  fully  illustrated. 

(a. )  In  the  case  of  secondary  qualities,  take,  for  ex- 
ample, the  secondary  quality — smell.  On  this  point 
Reid  makes  the  following  remarks:  "The  smell  of  a 
rose  signifies  two  things:  First,  a  sensation,  which  can 
have  no  existence  but  when  it  is  perceived,  and  can  only 
be  in  a  sentient  being  or  mind.  Secondly,  it  signifies 
some  power,  quality,  or  virtue,  in  the  rose,  or  in  efflu- 

*  "Works,"  Inq.,  p.  123;  I.  P.,  p.  314. 


TO    ITS    PHILOSOPHICAL    ANTECEDENTS.  33 

via  proceeding  from  it,  which  hath  a  permanent  exist- 
ence, independent  of  the  mind,  and  which,  by  the  con- 
stitution of  nature,  produces  the  sensation  in  us.  By 
the  original  constitution  of  our  nature  we  are  both  led  to 
believe  that  there  is  a  permanent  cause  of  the  sensation, 
and  prompted  to  seek  after  it:  and  experience  determines 
us  to  place  it  in  the  rose."  *  That  is,  sensations  of  smell 
and,  as  he  elsewhere  suggests,  those  of  taste,  sound,  etc., 
suggest  to  us  qualities  in  objects  as  the  causes  of  these 
sensations.  Thus  sensations  attended  by  suggestions  are 
perception  so  far  as  the  secondary  qualities  are  con- 
cerned. As  Hamilton  interprets  Reid  on  this  point: 
"In  a  sensation  (proper)  of  the  secondary  qualities,  as 
affections  in  us,  we  have  a  perception  (proper)  of  them 
as  properties  in  objects  and  causes  of  the  affections  in  us. "  f 
(b. )  In  the  case  of  primary  qualities  his  theory  of  per- 
ception as  sensations  attended  by  original  "  suggestions" 
and  beliefs  is  still  more  marked.  Take,  for  example, 
the  sense  of  touch.  Here  we  are  liable  to  confound  the 
sensation  and  the  quality  of  body  from  which  it  arises. 
The  sensation  is  only  a  "sign "of  a  quality  in  the  ex- 
ternal body:  but  we  are  wont  to  pass  quickly  from  the 
"  sign"  to  the  thing  signified  without  making  a  distinc- 
tion. There  is,  nevertheless,  a  distinction.  The  sensa- 
tion has  no  similitude  to  the  quality  known  as  hardness 
in  the  external  object.  How,  then,  do  we  come  to  have 
the  "conception"  and  "belief"  (perception)  of  the  ob- 
jective reality  of  what  we  call  hardness  in  body  ?  For  cer- 
tainly we  have  such  a  perception.  This  "  conception 

*  "Works,"  Inq.,  p.  114. 
f  Ibid.,  Note  D,  p.  884. 


34  RELATION    OF    REID'S    PHILOSOPHY 

and  belief,"  Reid  answers,  comes  to  us  in  the  following 
manner:  »"By  an  original  principle  of  our  constitution 
a  certain  sensation  of  touch  both  suggests  to  the  mind 
the  conception  of  hardness,  and  creates  the  belief  of  it: 
or,  in  other  words,  that  this  sensation  is  a  natural  sign 
of  hardness.  "*  Now  what  is  true  of  hardness  is  also  true 
of  softness,  roughness,  smoothness,  figure  and  motion. 
"All  these,"  says  Reid,  "by  means  of  corresponding 
sensations  of  touch,  are  presented  to  the  mind  as  real 
external  qualities;  the  conception  and  belief  of  them 
are  invariably  connected  with  the  corresponding  sensa- 
tions, by  an  original  principle  of  human  nature,  "f  The 
same  thing  is  true  in  regard  to  extension  and  figure. 
'  Our  perception  of  extension  and  figure  is  a  natural  sug- 
gestion attending  sensations  of  touch.  "Extension, 
therefore,  seems  to  be  a  quality  suggested  to  us,  by  the 
very  same  sensations  which  suggest  the  other  quali- 
ties above  mentioned  (i.  e.,  other  primary  qualities). 
When  I  grasp  a  ball  in  my  hand,  I  perceive  it  at  once 
hard,  figured  and  extended.  The  feeling  is  very  simple, 
and  hath  not  the  resemblance  to  any  quality  of  body. 
Yet  it  suggests  to  us  three  primary  qualities  perfectly 
distinct  from  one  another,  as  well  as  from  the  sensation 
which  indicates  them.  When  I  move  my  hand  along 
the  table,  the  feeling  is  so  simple  that  I  find  it  difficult 
to  distinguish  it  into  things  of  different  natures:  yet,  it 
immediately  suggests  hardness,  smoothness,  extension 
and  motion — things  of  very  different  natures,  and  all  of 
them  as  distinctly  understood  as  the  feeling  which  sug- 

*  "  Works,"  Inq.,  p.  121.  f  Ibid.,  Inqv  p.  123. 


TO    ITS    PHILOSOPHICAL    ANTECEDENTS.  35 

gests  them. "  *  It  is  apparent  from  the  above  quotations 
concerning  both  the  secondary  and  primary  qualities 
that  what  Reid  means  by  perception  is  sensations  at- 
tended by  original  "suggestions "in  the  form  of  "no- 
tions" or  "  conceptions  "  and  beliefs.  When  he  uses  the 
terms  "sign  '  and  "signify,"  he  means  simply  that  the 
sensation  is  a  "sign  "  of  a  quality  in  the  external  thing  ; 
and  what  he  means  by  this,  is  that  the  sensation  suggests  a 
"  notion"  or  "  conception"  of,  and  belief  in  the  existence 
of,  that  quality.  The  "notion  "  and  "conception"  are 
' '  suggestions  "  attending  sensations,  immediately  inspired 
by  the  constitution  of  our  nature.  The  "  belief"  in  the 
existence  of  the  quality  or  object  attending  sensations  is 
also  immediately  inspired  by  our  constitution.  Percep- 
tion, then,  according  to  Reid,  is,  as  was  suggested  in 
the  beginning,  sensations  attended  by  certain  original  , 
suggestions  and  beliefs.  Or,  to  put  the  definition  more 
nearly  in  his  own  language:  perception  is  the  "  notion  " 
or  "conception"  of  an  object,  together  with  a  belief  in 
its  existence;  which  "  notion  "  and  belief  are  originally 
"suggested"  or  "inspired"  by  the  constitution  of  our 
nature,  on  the  occasion  of  a  sensation  arising  in  the 
mind. 

The  foregoing  is  the  substance  of  Reid's  theory  of  per- 
ception as  we  find  it  developed  in  both  the  "  Inquiry" 
and  the  ' '  Intellectual  Powers. "  Two  questions  very  nat- 
urally suggest  themselves  here:  i.  Was  Reid  right  in 
attributing  the  "theory  of  ideas  "  to  preceding  philoso- 
phy? In  regard  to  this  question  there  is  a  differ- 
ence of  opinion.  Such  critics  of  Reid  as  Priestley,  f 

•"Works,"  Inq.,  pp.  124-5. 

f  "  Remarks  on  Reid,  Beattie,  and  Oswald,"  2d  ed.,  §  3,  p.  30. 


36  RELATION    OF    REID'S    PHILOSOPHY 

Brown,*  and  Webb  f  think  that  Reid  seriously  erred 
in  his  interpretation  of  the  large  majority  of  previ- 
ous systems  of  philosophy.  On  the  other  hand, 
Hamilton  J  comes  to  Reid's  defense,  and,  while  admit- 
ting him  to  be  mistaken  in  several  instances,  regards 
him,  especially  in  respect  to  modern  philosophy,  to 
have  good  grounds  for  ascribing  this  theory  to 
his  predecessors.  To  discuss  this  question  would 
require  a  survey  of  the  entire  history  of  philosophy, 
which,  of  course,  cannot  be  done  here.  If,  however, 
the  reader  desires  to  determine  the  correctness  of  Reid's 
interpretation,  I  will  be  pardoned  in  once  more  call- 
ing attention  to  the  fact  that  Reid's  conception  of  the 
"theory  of  ideas  "was  not  what  is  ordinarily  under- 
stood by  representative  perception.  The  theory  which 
he  ascribes  to  his  predecessors  is,  that  in  perception 
there  is  an  image  or  "  idea  "  existing  between  the  mind 
perceiving  and  the  existing  object — numerically  different 
from  both.  2.  From  all  that  is  said  upon  the  sub- 
ject, what  are  we  to  understand  Reid's  theory  of  per- 
ception really  to  be  ?  Is  it  the  theory  of  immediate  or  intui- 
tive perception — a.  direct  gaze  upon  extra-mental,  substan- 
tial objects;  or,  is  it  some  form  of  representative  percep- 
tion, only  one  form  of  which,  viz.,  the  tertium  quid  form, 
it  is  claimed  by  some,  he  really  combated  ?  Concerning 
this  question,  it  must  be  admitted  that  it  is  an  exceed- 
ingly difficult  task  to  determine  precisely  what  Reid's 
theory  of  perception  is.  This  difficulty  is  the  result  not 
only  of  the  looseness  of  his  presentation  of  the  subject, 

*  "  Philosophy  of  the  Human  Mind,"  lees,  xxvi,  xxvii. 
f  "  The  Veil  of  Isis,"  pp.  125-162. 
\  "Metaphysics,"  lees,  xxi,  xxii. 


TO    ITS    PHILOSOPHICAL    ANTECEDENTS.  37 

but  also  of  his  failure  to  fully  think  the  subject  through. 
By  some,  and  doubtless  by  the  majority  of  scholars  who 
have  given  Reid's  philosophy  thoughtful  consideration,, 
he  is  supposed  to  advocate  the  theory  of  immediate  per- 
ception. So  emphatically  do  they  affirm  this  to  be  his 
theory,  that  they  regard  it,  in  connection  with  his  doc- 
trine of  common  sense,  to  determine  his  historical  posi- 
tion or  significance.  By  others,  and  for  very  good  rea- 
sons, he  is  supposed  to  teach  some  form  of  representative 
perception.  This  form,  to  use  the  terminology  of  Ham- 
ilton, may  be  called  egoistical  representationism,  i.  e., 
the  object  before  the  mind  in  perception  is  a  subjective 
representative  object,  which  subjective  object  is  a  modi- 
fication of  the  mind.  And,  as  there  are  two  forms  of 
egoistical  representationism,  the  form  which  is  ascribed 
to  Reid  is:  that  the  subjective  object  is  really  identical  with 
the  perceptive  act,  but  logically  distinguished  from  if,  "being 
simply  the  perceptive  act  itself,  considered  in  one  of  its 
relations,  to  wit,  to  the  immediate  object,  the  reality  rep- 
resented, and  which,  in  and  through  that  representation 
alone,  is  objectified  to  consciousness  and  perceived."* 
As  has  been  suggested,  those  who  ascribe  some  form  of 
representative  perception  to  Reid,  have  good  grounds 
for  doing  so.  His  use  of  "notion,"  "conception," 
"suggestion,"  etc.,  certainly  is  favorable  to  an  interpre- 
tation of  his  teachings  in  favor  of  some  form  of  mediate, 
rather  than  immediate,  perception.  On  the  other  hand, 
there  are  good  reasons  for  believing  that  he  meant  to  teach 
the  doctrine  of  immediate  or  intuitive  perception.  Sir  Wm. 
Hamilton  has,  with  characteristic  thoroughness,  careful - 

•"  Works,"  Note  C,  p.  818. 


38  RELATION    OF    REID'S    PHILOSOPHY 

ly  selected  and  arranged  the  evidence  to  be  found 
in  both  the  "Inquiry"  and  the  "Intellectual  Powers" 
bearing  on  each  view  of  Reid's  theory  of  perception.  An 
examination  of  this  evidence  will  put  us  in  a  better  posi- 
tion to  come  to  some  conclusion  on  this  disputed  point* 
Following  the  order  of  Hamilton,  the  following  is  the 
substance  of  the  leading  arguments  in  favor  of  egoistical 
representationism  in  the  form  stated  above,  f 

I,  Reid's  doctrine  of  primary  qualities  implies  it.  He 
teaches  that  the  primary  qualities  of  body  are  sug- 
gested through  certain  sensations.  They  are  suggestions, 
or  conceptions,  immediately  arising  in  the  mind,  we 
know  not  how — by  a  natural  magic  as  it  were — on  oc- 
casion of  certain  sensations.  If  the  primary  qualities  are 
nothing  more  than  suggestions,  or  conceptions  "inspired 
by  a  means  unknown, "  then  they  are  only  representations  of 
it  knows  not  what,  blindly  determined  by  the  mind.  Per- 
ception is  simply  the  consciousness  of  these  concep- 
tions or  suggestions,  hence  our  knowledge  of  the  exter- 
nal world  would  certainly  not  be  immediate.  The  im- 
mediate object  before  the  mind  would  be  a  conception 
or  suggestion  and  not  an  extra-mental  object.  Hence 
Reid  must  be  considered  an  advocate  of  representative 
perception.  (Inq.,  pp.  122,  123,  128,  183,  188  ;  I.  P., 
pp.  258,  318,  320.)  This  argument,  somewhat  over- 
drawn by  Hamilton,  seems  to  me  to  be  one  of  the 
strongest  arguments  in  favor  of  Reid's  theory  being  that 
of  egoistical  representationism:  because  in  his  teach- 
ing, concerning  the  primary  qualities,  the  mind  has 
naught  but  sensations  accompanied  by  "suggestions" 

*  "  Works,"  Note  C,  pp.  819-24.         f   Ibid-i  Note  c»  P-  820-2. 


TO    ITS    PHILOSOPHICAL    ANTECEDENTS.  39 

or  "  conceptions"  to  deal  with.  Hamilton,  who  be- 
lieves Reid  to  hold  the  theory  of  immediate  perception, 
makes  a  plea  for  his  view  in  regard  to  this  point  by  say- 
ing, we  must  not  hold  Reid  too  rigidly  to  what  he  says 
in  the  "Inquiry"  on  the  subject  of  ''suggestion,"  as  he 
does  not  mention  it  in  the  "Intellectual  Powers,"  which 
would  seem  that  he  was  doubtful  of  its  tendency.  But 
this  plea,  to  my  mind,  has  little  force,  because,  in  the 
first  place,  Reid  did  not  retract  the  doctrine  of  "sug- 
gestion "in  the  "Intellectual  Powers  ; "  and,  in  the  second 
place,  although  he  does  not  use  the  word  "suggestion" 
in  the  "  Intellectual  Powers,"  his  theory  of  perception  in 
both  the  "Inquiry"  and  "Intellectual  Powers"  is 
essentially  the  same. 

2.  Intuitive  perception  implies  that  a  knowledge  and 
belief  of  the  existence  of  an  external  world  is  given  in 
perception,  and  there  is  no  need  of  resorting  to  "  natural 
magic,"  "inspiration,"  etc.,  to  explain  that  knowledge 
and  belief,  as  Reid  really  does.  In  the  case  of  cos- 
mothetic  idealism,  whose  theory  of  perception  is  repre- 
sentative perception,  in  which  "  the  mind  is  determined 
to  represent  to  itself  the  external  world,  which,  ex  hypo- 
thesi,  it  does  not  know,  the  fact  of  such  representation 
can  only  be  conceived  possible  through  some  hyper- 
physical  agency."  Now,  the  rationale  of  Reid's  theory 
of  perception — "natural  magic,"  "inspiration,"  "in- 
fused faith,"  etc., — rather  makes  a  representationist  than 
a  presentationist  out  of  him.  (Inq.,  122,  188;  I.  P., 

257.) 

There  is  certainly  some  force  in  the  above  argument, 
and  in  the  "Intellectual  Powers,"  Reid,  in  a  measure, 
approaches  the  Cartesian  doctrine  of  a  Deus  ex  machina 


40  RELATION    OF    REID'S    PHILOSOPHY 

in  his  remarks  on  perception.  (Seel.  P.,  p.  257.)  Even 
Hamilton  admits  this.  (See  note,  p.  257,  of  Reid's 
"Works,"  also  Note  C,  p.  821.) 

3.  Reid  equalizes  perception  and  imagination.  He 
speaks  of  imagination  as  a  faculty  of  immediate  know- 
ledge. Now  all  will  admit  that  in  an  act  of  the  imagina- 
tion the  external  object  is  known  only  mediately,  in  a 
representative  way.  Hence  Reid  must  have  meant  by 
ascribing  to  the  faculty  of  imagination  immediate  know- 
ledge, that  its  knowledge  is  not  representative  in  the 
tertium  quid  sense,  as  advocated  by  the  "theory  of 
ideas,"  but  that  it  is  really  mediate  in  the  sense  in  which 
we  ordinarily  speak  of  the  images  of  the  imagination  be- 
ing representative.  If  this  be  so,  in  the  case  of  the  im- 
agination, then  when  Reid  equalizes  perception  and 
imagination  by  attributing  to  both  of  them  immediate 
knowledge,  he  must  use  the  word  immediate  in  the  case 
of  perception,  just  as  he  uses  it  in  the  case  of  imagination, 
viz.,  immediate  in  opposition  to  mediate  as  advocated 
by  the  tertium  quid  theory,  but  nevertheless  mediate  in 
the  true  sense.  Or,  as  Hamilton  states  the  argument: 
"  In  calling  imagination  of  the  past,  the  distant,  etc.,  an 
immediate  knowledge,  Reid,  it  may  be  said,  could  only 
mean  by  immediate,  a  knowledge  effected  not  through 
the  supposed  intermediation  of  a  vicarious  object,  nu- 
merically different  from  the  object  existing  and  the  mind 
knowing,  but  through  a  representation  of  the  past,  or 
real,  object  in  and  by  the  mind  itself ;  in  other  words, 
that  by  mediate  knowledge  he  denoted  a  non-egoistical, 
by  immediate  knowledge  an  egoistical,  representation. 
This  being  established,  it  may  be  further  argued — that  in 
calling  perception  an  immediate  knowledge,  he,  on  the 


tO   ITS    PHILOSOPHICAL    ANTECEDENTS.  41 

same  analogy,  must  be  supposed  to  deny,  in  reference  to 
this  faculty,  only  the  doctrine  of  non-egoistical  represen- 
tation. This  is  confirmed  by  his  not  taking  the  distinc- 
tion between  perception  as  a  presentative,  and  memory, 
for  instance  (i.  e.,  recollective  imagination),  as  a  repre- 
sentative cognition  :  which  he  ought  to  have  done,  had 
he  contemplated,  in  the  former,  more  than  a  faculty, 
through  which  the  ego  represents  to  itself  the  non-ego, 
of  which  it  has  no  consciousness — no  true  objective  and 
immediate  apprehension."  *  (Inq.,  p.  106;  I.  P.,  pp. 
226,  233,  292,  293,  etc.) 

Hamilton  tries  to  lessen  the  force  of  this  argument 
by  saying  that  it  merely  ' '  proves  that  Reid's  perception 
may  be  representative,  not  that  it  actually  is  so."f  How- 
ever, when  taken  in  connection  with  the  preceding  argu- 
ments, it  at  least  shows  that  the  logical  implication  of 
Reid's  presentation  of  his  theory  of  perception  is  repre- 
sentationism. 

4.  Reid,  in  some  instances,  seems  to  make  perception 
the  result  of  inference,  so  that  the  remote  cause  is  the 
object  perceived,  and,  hence,  not  the  immediate  object 
of  perception.  Hence  perception  cannot  be  immediate. 
(Inq.,  p.  125;  I.  P.,  259,  260,  309,  326,  328.) 

This  argument  has  weight.  Reid  seems  to  teach  that 
perception  is  the  result  of  inference,  thus  making  it 
mediate  instead  of  immediate.  However,  it  must  be 
taken  into  consideration,  that  there  are  other  passages  in 
which  he  expressly  denies  that  perception  is  the  result 
of  inference.  (I.  P.,  259,  260,  309,  326,  328.) 

There  are  several  minor  arguments  favoring  this  inter- 

*  "  Works,"  Note  C,  pp.  821-822.  f  Ibid.,  p.  822. 


42  RELATION    OF    REID*S    PHILOSOPHY 

pretation  of  Reid,  but  they  are  hardly  of  sufficient  im- 
portance to  be  noticed  here.*  On  the  other  hand,  let  us 
state  the  evidence  favoring  the  interpretation  of  Reid's 
theory  of  perception  as  immediate  perception,  f 

1.  "  Knowledge   and  existence  only  infer  each  other 
when  a   reality  is  known  itself  or  as  existing."     That  is, 
knowledge  and  existence  are  only  convertible  when  there 
is  a  knowledge  of  reality  in  itself.     It  is  only  under  such 
conditions  that  we  can  say  that  the  reality  "is   known 
because  it  exists,  and  exists  since  it  is  known. "     This  is 
what  constitutes  an  immediate  perception.      Now  Reid's 
teaching  is  in  harmony  with  the   above   position.     He 
says:   "It  seems  admitted    as   a  first   principle,  by   the 
learned  and  unlearned,   that  what  is  really   perceived 
must  exist,  and  that  to  perceive  what  does  not  really  exist 
is  impossible. "  (I.  P.,  p.  274.) 

2.  All  philosophers  agree  that  the  idea  or   representa- 
tive object  is  immediately  apprehended,  and  that  as  thus 
apprehended  it  exists  ne.cessarily.     Now  if  Reid  affirms 
that  external  objects  are  perceived  not   less  immediately 
he  must  be  regarded  as  holding  the  theory  of  immediate 
perception.     This  he  affirms.     (I.   P.,    263,    272,    274, 
289,  446.) 

3.  All  admit  that  mankind  at   large  believe  that  the 
external  reality  is  the  immediate   object  of  perception. 
Mankind,  in  general,  take  the    "common- sense"  view 
of  the  world— i.  e.,  they  believe  in  the  existence  of  a  world 
of  substantial  "things,"  which  "  things  "  are  immediate- 
ly  perceived.     Only  philosophers  affirm  the  contrary. 

•  Reid's  "  Works,"  Note  C,  pp.  821-2. 
f  Ibid.,  pp.  822-3. 


TO  ITS  PHILOSOPHICAL  ANTECEDENTS.  43 

Now  Reid  affirms  himself  to  be  on  the  side  of  mankind 
in  general — or,  as  he  suggests,  on  the  side  of  the  vulgar, 
in  this  respect.  (I.  P.,  275,  284,  298,  299,  302.) 

This  argument  certainly  has  great  force.  Reid  refers 
frequently  to  the  view  of  the  "  vulgar,"  which  is  the  be- 
lief that  in  perception  we  gaze  immediately  upon  an  ex- 
ternal world  of  "  things,"  and  then  places  himself  on  the 
side  of  the  "  vulgar."  (See  above  references.) 

4.  Reid  affirms,  that  in  self-consciousness  we  have  an 
immediate  knowledge  of  the  modifications  of  self:  and 
adds,  that  in  perception  we  have  knowledge  just  as 
immediate  of  the  qualities  of  the  "not-self."  (I.  P., 
263,  269,  373.) 

Thus  runs  the  evidence  in  favor  of  both  interpreta- 
tions. It  is  apparent  at  once  that  there  are  good 
grounds  for  holding  either  view.  Sir  Wm.  Hamilton 
and  most  interpreters,  for  the  reasons  above  mentioned, 
think  that  Reid  really  held  the  theory  of  immediate  per- 
ception. Brown,  Webb,  and  Ferrier  think  his  theory 
was  a  theory  of  representative  perception — egoistical 
representationism.  When  the  doctors  disagree,  who  shall 
decide  ?  It  is  quite  evident,  from  a  consideration  of 
the  above  evidence,  that  it  is  not  well  to  dogmatically 
affirm  either  view.  My  own  opinion  is,  that  Reid  meant 
to  teach  natural  realism,  with  its  theory  of  immediate 
perception;  but  his  presentation  of  the  subject  is  so 
loose,  owing  to  a  looseness  of  language  and  a  failure  to 
fully  think  the  subject  through,  as  to  afford  good 
grounds  for  supposing  him  to  teach  cosmothetic  ideal- 
ism, with  its  theory  of  egoistical  representationism. 
This  is  the  only  way  that  Reid  can  be  saved  from  self- 
contradiction. 


44  RELATION  OF  REID'S  PHILOSOPHY 

Let  us  now  proceed  to  the  second  feature  of  Reid's 
philosophy — his  doctrine  of  common  sense.  Not  only 
did  Reid  oppose  to  scepticism  his  theory  of  immediate 
perception,  to  subvert  the  ' '  theory  of  ideas, "  on  which 
he  supposed  this  scepticism  to  be  based;  but  he  also  es- 
tablished his  organon  of  common  sense  as  authority  for 
the  acceptance  of  certain  fundamental  principles  which 
this  scepticism  denied.  Reid  used  this  term  in  a  rather  am- 
biguous way,  and  often  in  such  a  way  as  to  mislead  the 
reader  as  to  his  real  meaning.  Especially  careless  is  he 
in  the  use  of  the  term  in  the  "Inquiry,"*  where  he  lays 
himself  open  to  an  interpretation  which  is  really  opposed 
to  his  real  meaning — particularly  as  indicated  in  the 
"  Intellectual  Powers. "  f  Reid  is  sometimes  supposed 
to  mean  by  common  sense,  the  undeveloped  belief  of 
the  masses,  which  he  would  oppose  to  the  reasonings  of 
philosophers.  Again,  he  is  supposed  to  mean  by  the 
term  "good  sense," — sound  understanding.  Even  Kant 
was  misled  in  thus  interpreting  Reid.  J  Sometimes  he  is 
thought  to  mean  the  voice  of  the  majority,  or  uni- 
versal assent.  But,  while  his  carelessness  lays  some  of 
his  remarks  open  to  such  interpretations,  a  critical  study 
of  his  works  reveals  the  fact,  that  what  he  really  means 
by  the  principles  of  common  sense  is,  the  self-evident  prin- 
ciples of  reason;  ws\&  what  he  means  by  common  sense  is' 
the  faculty  of  such  principles ;  or,  reason  judging  self-ev- 
ident truth.  This  is  quite  evident  from  the  following 
statements,  taken  both  from  the  "Inquiry"  and  the 
"Intellectual  Powers": — 

*  P-  101.  f  p.  425. 

f  "  Prolegomena,"  pp.  4-6. 


TO   ITS   PHILOSOPHICAL   ANTECEDENTS.  45 

"If  there  be  certain  principles,  as  I  think  there  are, 
which  the  constitution  of  our  nature  leads  us  to  believe, 
and  which  we  are  under  a  necessity  to  take  for  granted 
in  the  common  concerns  of  life,  without  being  able  to 
give  a  reason  for  them;  these  are  what  we  call  the 
principles  of  common  sense  ;  and  what  is  manifestly  con- 
trary to  them  is  what  we  call  absurd. "  *  "  It  is  absurd  to 
conceive  that  there  can  be  any  opposition  between  reason 
and  common  sense.  It  is  indeed  the  firstborn  of  reason: 
and,  as  they  are  commonly  joined  together  in  speech  and 
in  writing,  they  are  inseparable  in  their  nature  We 
ascribe  to  reason  two  offices,  or  two  degrees.  The  first 
is  to  judge  of  things  self-evident;  the  second  to  draw  con- 
clusions that  are  not  self-evident  from  those  that  are. 
The  first  of  these  is  the  province,  and  the  sole  province, 
of  common  sense:  and,  therefore,  it  coincides  with  reason 
in  its  whole  extent,  and  is  only  another  name  for  one 
branch  or  one  degree  of  reason,  "f  The  self-evident 
principles  of  reason,  then,  are  what  Reid  means  by  com- 
mon-sense principles;  and  by  common  sense  he  means 
reason  declaring  self-evident  truth.  It  will  appear,  also, 
from  the  above  citations,  that  the  criteria  of  common- 
sense  principles,  with  Reid,  are,  necessity  and  self-evi- 
dence. 

Reid,  however,  was  very  unfortunate  in  his  classification 
of  these  principles.  He  places  on  the  list  of  common- 
sense  principles,  truths  which  are  nothing  more  than 
mere  generalizations  of  experience.  His  loose  classifica- 
tion has  had  considerable  to  do  in  bringing  condemnation 
upon  his  philosophy.  J 

*  "Works,"  Inq,,  p.  108.  f  "Ibid.,  I.  P.,  p.  425. 

J  Ibid.,  I.  P.,  pp.  434-468. 


46  RELATION  OF  REID'S  PHILOSOPHY. 

The  historical  significance  of  Reid's  philosophy,  then, 
lies  in  calling  into  question  the  "  theory  of  ideas"  on 
which  the  scepticism  of  Hume  is  founded,  and  in  op- 
posing to  it  the  theory  of  immediate  perception,  and  the 
organon  of  common  sense. 

*  «  Works,"  I.  P.,  pp.  441-461. 


THE   INFLUENCE   OF   REID'S   PHILOSO- 
PHY  UPON   SUBSEQUENT   PHILO- 
SOPHIC  THOUGHT. 

CONTEMPORANEOUS  with  Reid,  and  influenced  by  him, 
were  James  Oswald  *  and  James  Beattie,f  also  exponents 
of  the  doctrine  of  common  sense.  Both  adhered  more 
slavishly  to  the  doctrine  than  Reid.  Oswald,  in  his 
"Appeal,"  virtually  uses  the  same  argument  which  is 
used  by  Reid,  so  far  as  the  validity  of  so-called  funda- 
mental truths  is  concerned.  Common  sense  discerns  and 
vouches  for  all  fundamental  truths.  It  is  reason  de- 
claring self-evident  truth.  Now  just  as  common  sense 
declares  self-evident  truth  in  other  departments  of 
thought,  so  it  declares  primary  truths  in  the  domain  of 
morals  and  religion.  In  endeavoring  to  strengthen  the 
argument  from  common  sense  he  makes  use  of  the 
reductio  ad  absurdum.  Beattie's  ' '  Essay  "  was  called 
forth  specially  by  the  scepticism  of  Hume.  In  it,  with 
Reid,  he  opposes  the  affirmations  of  common  sense  to 
scepticism.  He  holds  to  the  validity  of  so-called 
primary  truths.  Our  ground  for  accepting  them  is  their 

*  "  An  Appeal  to  Common  Sense  in  behalf  of  Religion,"  London, 
1766-72. 

f  "  Essay  on  the  Nature  and  Immutability  of  Truth  in  Opposition 
to  Sophistry  and  Scepticism,"  4th  ed.,  London,  1773. 


48  THE  INFLUENCE  OF  REID'S  PHILOSOPHY 

own  self-evidence.     So  that  his  doctrine  is  essentially 
the  same  as  Reid's. 

The  real  successorof  Reid  was  Dugald  Stewart.*  He, 
too,  is  in  substantial  harmony  with  the  views  of  Reid. 

1.  He  agrees  with  him  in  regard  to  the  method  which 
ought  to  be  adopted  in  studying   the  phenomena  of  the 
human  mind — the  inductive  method,  f 

2.  In  his  theory  of  perception  he  is   in   substantial 
agreement  with  Reid.     He  regards  perception  as  the 
"notion  "  of  an  object,  which  notion  and  belief  are  in- 
stinctively suggested  or  inspired  on  the  occasion  of  sen- 
sation. J     Like  Reid,  he  doubtless  meant  to  teach  imme- 
diate perception,  but,   unfortunately,    did   not   succeed 
much  better  than  Reid  in  clearing  his  doctrine  of  those 
inconsistencies  and  ambiguities  which  render  the  theory 
capable  of  a  two-fold  interpretation.     That  is,  although 
he  doubtless   meant  to  teach  the  theory  of  immediate 
perception  common   to  natural   realism,    his   presenta- 
tion of  the  subject  involves  egoistical  representationism. 

3.  With  respect  to   his  doctrine  of  commojL-Sfinse, 
we  find  him  also  in  substantial  agreement  with  Reid. 
However,  Stewart  did  not  like  the  term — "  the  principles 
of  common  sense,"  thinking  it  open  to  serious  objections, 
because  of  its  associations  and  ambiguity.     For  this  term 
he  substituted  the  expression:   "  the  fundamental  laws 
of  human  belief."     These   laws   he   considered     "the 
constituent    elements    of    reason."     This   doctrine    he 
emphasized  just  as  much  as  Reid  did,  and  he  saw  in  it 

*  "  Collected  Works,"  ed.  by  Hamilton,  Edinburgh,  1854-60. 
f  Ibid.,  vol.  ii,  Int.,  §§  i  and  2. 
J  Ibid.,  vol.  ii,  ch.  i. 


UPON  SUBSEQUENT  PHILOSOPHIC  THOUGHT.  49 

the  only  true  organon  for  philosophy,   and  the  antidote 
for  scepticism.  * 

Dr.  Thomas  Brown,  f  was  also,  to  a  certain  extent,  a 
disciple  of  Reid.  Influenced,  however,  by  the  teach- 
ings of  Hartley,  and  the  sensationalism  of  the  French 
Ideologists,  he,  in  a  measure,  deviated  from  some  of  the 
positions  of  the  Scottish  School.  This  is  especially 
manifest  in  his  analysis  and  classification  of  the  pheno- 
mena of  the  mind.  Reid  and  Stewart  being  emphati- 
cally opposed  to  sensationalism,  did  not  carry  their  psy- 
chological analysis  as  far  as  they  doubtless  would  have 
done,  had  not  sensationalism  been  such  a  bugbear  to 
them.  Brown,  however,  was  not  to  be  so  easily  fright- 
ened, and  he  carried  his  analysis  to  a  greater  simplifica- 
tion. He  tried  to  unite  some  of  the  positions  of  the 
Sensational  School  with  certain  positions  of  the  Scot- 
tish School. 

1.  His  method  was  that  of  the  Scottish  School,  viz., 
the  inductive  method.     He  insisted  upon,  applying  the 
method  adopted  by  physical  science.  J 

2.  The  result  of  an  application  of  this  method  was  a 
reduction  of  the  number  of  original  faculties  to  which 
Reid  and  Stewart   held,  and  the  resolving  of  all  mental 
phenomena  into  modifications  of  the  mind  itself.  § 

3.  His  theory  of  perception  differs  from  the  theory  of 
Reid  and  Stewart.     It  is  egoistical  representationism,  i.  e., 

*  "Collected  Works,"  vol.  iii,  ch.  i. 

f  "Lectures  on  the  Philosophy  of  the  Human  Mind,"  Hallowell, 
1829. 

J  Ibid.,  lees,  ix,  x,  xi. 
§  Ibid.,  lees,  xvi,  xvii. 


50  THE   INFLUENCE  OF  REID'S   PHILOSOPHY 

the  object  before  the  mind  in  perception  is  not  an  extra- 
mental,  material  object,  but  a  mental  object,  which  ob- 
ject is  merely  a  modification  of  the  mind  itself."* 

4.  On  what  authority,  then,  do  we  believe  in  an  ex- 
ternal world?  Brown  answers:  through  the  intuitive 
principle  of  causation,  we  are  led  to  infer  the  existence 
of  an  external  world.  On  occasion  of  certain  sensations 
arising  in  the  mind,  we  infer  an  extra-mental  reality  as 
their  cause,  which  external  cause  he  affirmed  to  be  an 
extended,  material  object  f 

Brown,  then,  retreats  from  natural  realism  with  its 
doctrine  of  immediate  perception,  and  goes  over  to 
cosmothetic  idealism,  with  its  doctrine  of  mediate 
perception — affirming,  however,  the  existence  of  an 
external,  material  world  on  the  strength  of  the  causal 
principle. 

In  Sir  William  Hamilton^  we  have  the  ablest  expo- 
nent and  special  defender  of  the  Scottish  realism.  To 
fully  appreciate  his  philosophy,  as  Dr.  McCosh  suggests, 
we  must  bear  in  mind  the  influence  of  four  men  upon 
his  thinking:  Aristotle,  Reid,  Kant,  and  Jacobi.  Our 
interest  here  extends  only  to  the  influence  exerted  upon 
his  philosophical  thinking  by  Reid.  This  is  manifest  in 
his  theory  of  perception  and  his  doctrine  of  common 
sense. 

i.   His  theory  of  perception   is  intuitive  or  immediate 

*  "  Lectures  on  the  Philosophy  of  the  Human  Mind,"  Hallo  well, 
1820,  lees,  xxv-xxvii. 

f  Ibid. 

J  "Lectures  on  Metaphysics,"  Edinburgh  and  London,  1870;  Cf. 
also  Reid's  "  Works,"  Notes  and  Dissertations, 


UPON  SUBSEQUENT  PHILOSOPHIC  THOUGHT.  51 

perception.*  The  mind  gazes  immediately  upon  extra- 
mental  reality.  He  differs  from  Reid,  however,  in  ex- 
cluding from  the  objects  immediately  known,  objects 
which  are  not  in  correlation  to  the  bodily  organism. 
According  to  Hamilton,  the  objects  which  the  mind 
immediately  perceives  in  sense-perception  are  the  organ- 
ism, and  the  extra-bodily  objects  in  correlation  to  the 
organism,  i.  e.,  extra-bodily  objects  in  their  resistance 
to  our  locomotive  or  muscular  energy,  f  The  grounds 
on  which  he  bases  the  theory  of  immediate  perception 
are,  positively,  the  testimony  of  consciousness,  J  and, 
negatively,  the  sceptical  consequences  which  he  regards 
to  be  the  inevitable  result  of  a  denial  of  this  theory.  § 

2.  Reid's  influence  upon  Hamilton  is  very  marked 
indeed  in  his  doctrine  of  common  sense.  Hamilton 
made  an  elaborate  attempt  not  only  to  establish  the 
legitimacy  of  the  argument  from  common  sense,  and  to 
point  out  the  criteria  of  common-sense  principles,  but 
also  to  vindicate  the  use  of  the  term  "common  sense.' 
The  propriety  of  using  the  term"  common  sense  "  he  tries 
to  establish  by  an  appeal  to  the  history  of  philosophy. 
He  traces  the  use  of  the  word  "  from  the  dawn  of  specu- 
lation to  the  present  day,"  finding  it  in  use  by  nearly 
every  philosopher.  This  historical  survey  evinces  a 
patience  and  erudition  which  are  simply  remarkable. 

*  "  Metaphysics,"  vol  ii,  lees,  xxiv-xxviii,  also  Reid's  "  Works," 
Note  D. 

f  Ibid.  See  in  Note  D  other  differences  of  a  minor  character, 
pp.  882-6. 

I  Ibid. 

§  Reid's  "Works,  "Note  A. 


52  THE  INFLUENCE  OF   REID'S   PHILOSOPHY 

In  the  works  of  one  hundred  and  six  writers,  he  finds 
witnesses  to  the  legitimacy  of  the  term  "  common  sense." 
Among  these  writers  are  numbered  the  greatest  names 
in  philosophy.  As  to  the  meaning  and  authority  of 
common  sense  he  says: 

Demonstration,  if  proof  be  possible  at  all,  must 
ultimately  rest  upon  certain  fundamental  propositions 
which  must  be  accepted.  These  propositions  are  more 
on  the  order  of  facts,  feelings,  beliefs,  than  cognitions, 
because  of  their  inexplicable  character.  Nevertheless, 
Hamilton  calls  them  cognitions.  Now,  if  they  must  be 
accepted,  the  question  arises  as  to  the  authority  for 
accepting  them.  The  answer  to  this  is:  they  must  be 
accepted  because  they  are  the  conditions  sine  qua  non  of 
knowledge,  and  to  impeach  them  is  to  impeach  the  data 
of  consciousness.  To  show  that  a  denial  of  a  certain 
proposition  would  impeach  the  integrity  of  an  original 
datum  of  consciousness,  is  to  argue  from  common 
sense.  "Limiting,  therefore,  our  consideration  to  the 
question  of  authority:  how,  it  is  asked,  do  these  pri- 
mary propositions — these  cognitions  at  first  hand — these 
fundamental  facts,  feelings,  beliefs,  certify  us  of  their 
own  veracity  ?  To  this  the  only  possible  answer  is — 
that  as  elements  of  our  mental  constitution — as  the 
essential  conditions  of  our  knowledge — they  must  by  us 
be  accepted  as  true.  To  suppose  their  falsehood,  is  to 
suppose  that  we  are  created  capable  of  intelligence,-  in 
order  to  be  made  the  victims  of  delusion:  that  God  is  a 
deceiver,  and  the  root  of  our  nature  a  lie.  But  such  a 
supposition,  if  gratuitous,  is  manifestly  illegitimate. 
For,  on  the  contrary,  the  data  of  our  original  conscious- 
ness must,  it  is  evident,  in  the  first  instantt  be  presumed 


UPON  SUBSEQUENT  PHILOSOPHIC  THOUGHT.  53 

true.  It  is  only  if  proved  false,  that  their  authority  can, 
in  consequence  of  that  proof,  be,  in  the  second  instance, 
disallowed.  Speaking,  therefore,  generally,  to  argue 
from  common  sense  is  simply  to  show,  that  the  denial 
of  a  given  proposition  would  involve  the  denial  of  some 
original  datum  of  consciousness:  but  as  every  original 
datum  of  consciousness  is  to  be  presumed  true,  that  the 
proposition  in  question,  as  dependent  on  such  a  prin- 
ciple, must  be  admitted."* 

But  still  it  may  be  urged:  Why  trust  the  deliverances 
of  consciousness  ?  To  this  question  Hamilton  replies: 
"If,  therefore,  it  can  be  shown  on  the  one  hand,  that 
the  deliverances  of  consciousness  must  philosophically 
be  accepted,  until  their  certain  or  probable  falsehood 
has  been  positively  evinced:  and  if,  on  the  other  hand, 
it  cannot  be  shown  that  any  attempt  to  discredit  the 
veracity  of  consciousness  has  ever  yet  succeeded:  it 
follows  that,  as  philosophy  now  stands,  the  testimony  of 
consciousness  must  be  viewed  as  high  above  suspicion, 
and  its  declarations  entitled  to  demand  prompt  and  un- 
conditional assent,  "f 

In  regard  to  the  first  point  it  must  be  acknowledged 
that,  at  least,  in  the  first  instance,  the  veracity  of  con- 
sciousness must  be  accepted.  We  may  not  gratuitously 
assume  that  Nature  works  "in  counteraction  of  her- 
self. "  Unless  there  are  reasons  to  the  contrary,  it  is  not 
to  be  supposed  that  our  faculty  of  knowledge  is  "an 
instrument  of  illusion." 

But,  secondly,  even  though  in  the  outset  the  veracity 
of  the  deliverances  of  consciousness  must  be  admitted, 

*  «  Works,"  Note  A,  p.  743.  t  Ibid.,  p.  745. 


54  THE  INFLUENCE   OF   REID'S   PHILOSOPHY 

' '  it  still  remains  competent  to  lead  a  proof  that  they  are 
undeserving  of  credit."  The  question,  however,  arises 
as  to  how  this  is  to  be  accomplished.  This  can  only 
be  done  (i)  by  showing,  inasmuch  as  there  are  quite  a 
number  of  these  primary  data,  that  they  immediately 
contradict  each  other,  or  (2)  that  they  are  indirectly  con- 
tradictory, inasmuch  as  conclusions  derived  from  them, 
and  for  which  they  are  responsible,  are  mutually  con- 
tradictory. This  would  prove  the  inconsistency  of  con- 
sciousness with  itself,  and,  of  course,  as  a  consequence, 
its  inconsistency  with  the  unity  of  truth.  But  such  con- 
tradiction or  inconsistency,  says  Hamilton,  has  never 
yet  been  established.  "No  attempt  to  show  that  the 
data  of  consciousness  are  (either  in  themselves,  or  in 
their  necessary  consequences)  mutually  contradictory, 
has  yet  succeeded:  and  the  presumption  in  favor  of  the 
truth  of  consciousness  and  the  possibility  of  philosophy 
has  therefore,  never  been  redargued.  In  other  words, 
an  original,  universal,  dogmatic  subversion  of  knowledge 
has  hitherto  been  found  impossible. "  *  We  must,  then, 
accept  the  primary  deliverances  of  consciousness  as  true, 
and  the  argument  from  common  sense  which  shows  that 
a  denial  of  a  certain  proposition  discredits  an  original 
datum  of  consciousness  must  be  regarded  as  legitimate. 
The  essential  marks  which  distinguish  these  original 
or  fundamental  cognitions  or  convictions  from  those 
which  are  derived,  are  four,  viz.,  incomprehensibility, 
simplicity,  necessity  and  absolute  universality,  and  com- 
parative evidence  and  certainty.  A  conviction  is  in- 
comprehensible when  it  is  merely  given  in  consciousness 

*  "  Works,"  Note  A,  p.  746. 


UPON  SUBSEQUENT  PHILOSOPHIC  THOUGHT.  55 

that  its  object  is,  and  not  why  or  how  it  is.  A  cognition 
or  belief  is  simple  when  it  is  not  compounded  of  other 
cognitions  or  beliefs.  A  cognition  or  belief  is  necessary 
or  universal  (these  are  coincident)  when  it  is  impossible 
to  think  it  false.  By  comparative  evidence  and  cer- 
tainty is  meant,  quoting  from  Aristotle,  "If  we  know 
and  believe  through  certain  original  principles,  we 
must  know  and  believe  these  with  paramount  certainty, 
for  the  very  reason  that  we  know  and  believe  all  else 
through  them."  These  four  marks,  then,  incompre- 
hensibility, simplicity,  necessity  and  absolute  universality, 
and  comparative  evidence  and  certainty,  constitute  the 
essential  characters  by  which  original  cognition  or  beliefs 
are  known.*  Common-sense  principles,  then,  are  in- 
comprehensible, simple,  necessary,  and  absolutely  uni- 
versal -principles,  which  if  an  attempt  be  made  to  prove 
or  disprove  them  would  involve  a  resort  to  principles 
"neither  more  evident  nor  more  certain." 

Hamilton  made  no  such  attempt  as  that  of  Reid's  to 
classify,  or  to  make  a  list  of,  these  principles.  However, 
he  emphatically  pronounces  the  immediate  perceptions 
of  self  and  of  an  extra-mental  world  of  extended  objects 
to  be  common-sense  principles,  for  they  are  primary  data 
of  consciousness. 

Our  interest  here  in  Hamilton's  philosophy,  as  before 
suggested,  does  not  extend  beyond  his  theory  of  per- 
ception and  his  doctrine  of  common  sense.  These  are 
the  features  which  ally  him  to  Reid  and  the  Scottish 
School.  These  we  have  found  to  be  immediate  or 
intuitive  perception  and  the  veracity  of  consciousness  in 

*  "Works,"  Note  A,  p.  754;  "  Metaphysics,"  lee.  xxxviii. 


56  THE  INFLUENCE  OF  REID'S  PHILOSOPHY 

its  original  deliverances  in  the  form  of  "cognitions"  or 
"beliefs." 

In  France,  the  philosophy  of  Reid  exerted  considera- 
ble influence.  It  was  first  used  by  M.  Royer-Collard  * 
as  a  weapon  against  sensationalism  and  materialism. 
The  philosophy  of  Condillac  and  the  French  Ideolo- 
gists was  strongly  established  there.  Collard  saw  that 
the  sensationalism  of  Condillac  rested  upon  the  same 
foundation  as  that  which  underlay  the  scepticism  of 
Hume;  and,  with  Reid,  he  felt  that  if  the  premises  be 
accepted  the  conclusion  legitimately  followed.  The  prem- 
ises of  scepticism  and  sensationalism  are  the  same,  the 
"theory  of  ideas."  The  same  means  which  Reid  used 
for  the  overthrowal  of  these  premises  were  used  by  Col- 
lard — the  theory  of  immediate  perception  and  the  prin- 
ciple of  common  sense — meaning  by  common  sense  a 
sort  of  mental  instinct. 

Another  French  philosopher  on  whose  thinking  Reid's 
philosophy  exerted  considerable  influence  was  M.  Victor 
Cousin,  f  the  real  father  of  eclecticism  in  France.  He  bor- 
rows largely  from  the  Scottish  and  German  schools  of 
philosophy,  but  acknowledges  the  principal  factor  of  this 
eclecticism  to  be  taken  from  the  Scottish  philosophy. 
In  the  adoption  of  the  inductive  method,  in  basing  phi- 
losophy upon  psychology,  in  the  use  of  the  doctrine  of 
common  sense  in  a  modified  form,  we  see  the  in- 
fluence of  Reid's  philosophy  upon  the  thinking  of 
Cousin. 

*  "  Fragmens  de  Royer-Collard,"  Jouffroy's  trans,  of  the  works 
of  Reid. 

t  "Philosophic  Ecossaise,"  Paris,  1846. 


UPON  SUBSEQUENT    PHILOSOPHIC  THOUGHT.  57 

Th.  Jouffroy,*  the  pupil  of  Cousin,  was  also  greatly 
influenced  by  Reid's  philosophy.  He  translated  the 
works  of  Reid  into  French,  and  it  was  through  his 
teaching,  together  with  the  teaching  of  Collard  and 
Cousin,  that  the  Scottish  philosophy  became  for  a 
while  the  prevailing  philosophy  in  France.  He,  too, 
is  an  eclectic,  but  some  of  the  positions  of  the  Scottish 
School  are  prominent  factors  in  his  eclecticism.  The 
application  of  the  inductive  method  to  the  study  of  the 
phenomena  of  consciousness,  and  the  common-sense  at- 
titude toward  the  problem  of  substance,  indicate  the  in- 
fluence of  Reid  and  Stewart  upon  his  thinking,  f 

In  Germany,  Reid's  influence  upon  philosophy 
amounts  to  very  little  indeed.  Kant  regarded  his  phi- 
losophy with  more  or  less  contempt.  There  are  some 
evidences  of  its  influence  in  the  philosophy  of  Benecke.  J 

In  America,  directly  and  indirectly  (through  his  dis- 
ciples) Reid's  philosophy  has  exerted  great  influence. 
Dr.  Porter  says:  ''The  Scottish  philosophy  has  had  a 
wide-spread  influence  in  this  country.  The  works  of 
Reid  were  not  so  generally  circulated  on  account  of  the 
pre-occupations  of  the  American  War  for  Independence 
and  the  organization  of  the  new  political  union,  1770- 
1800,  but  when  the  attention  of  thinking  men  was 
aroused  to  the  practical  consequences  of  the  theological 
and  political  philosophy  of  England  and  France,  the 
works  of  Reid  were  studied  for  a  better  system.  As 
soon  as  Dugald  Stewart  appeared  upon  the  arena,  his 


*  "  Preface  a  la  Traduction  des  CEuvres  de  Reid,"  1835. 
f  Cf.  McCosh,  "  The  Scottish  Philosophy,"  pp.  302-3. 
J  "  Die  Neue  Psychologic,"  Berlin,  1845. 


58  THE  INFLUENCE  OF  REID'S  PHILOSOPHY 

lectures  were  resorted  to  by  a  few  favored  American 
pupils,  and  his  works  were  reprinted  as  fast  as  they  ap- 
peared, and  some  of  them  became  the  favored  text- 
books in  our  leading  colleges."*  Later,  through  the 
works  of  Hamilton,  widely  circulated  in  this  country, 
and  the  works  of  prominent  American  thinkers  identi- 
fied with  the  Scottish  School,  the  essential  principles  of 
Reid's  philosophy  became  widely  known,  being  taught 
in  many  colleges.  Among  the  American  writers  on 
philosophy,  just  referred  to,  Dr.  James  McCosh  and  Dr. 
Noah  Porter  may  be  mentioned.  McCosh,  f  though  differ- 
ing from  Reid  in  points  of  minor  importance,  accepts  with 
slight  alterations  the  cardinal  features  of  his  philosophy. 

i.  His  theory  of  perception  is  intuitive  or  immediate 
perception.  In  sense-perception  we  have  an  immediate 
knowledge  of  extra-mental  material  objects.  |  These 
objects  are  the  bodily  organism,  the  various  parts  of 
which  "  as  affected  "  are  immediately  perceived  through 
the  different  senses;  and  extra-bodily  material  objects  in 
correlation  to  the  body,  perceived  specially  through  the 
muscular  sense. 

"We  may  notice  here  that  sense-perception  gives  us 
(i)  Externality.  We  perceive  all  material  objects  as 
out  of,  and  independent  of,  the  perceiving  mind.  This 
is  associated  with  (2)  Extension.  We  perceive  things 
as  extended  by  all  the  senses,  not  only  as  Locke  thought 
by  sight  and  touch,  but  by  smell,  taste  and  hearing  ;  by 

*  "Ueberweg's  History  of  Philosophy,"  Appendix  i,  vol.  ii, 
pp.  451-2- 

f  "  Psychology,"  New  York,  1886;  "  Realistic  Philosophy,"  New 
York,  1887,  2  vols.,  etc.  J  "Psychology,"  pp.  20-69. 


UPON  SUBSEQUENT  PHILOSOPHIC  THOUGHT.  59 

all  these  we  know  our  affected  organism  as  in  a  certain 
direction  and  so  in  space ;  by  taste  and  smell  we  know 
the  palate  and  nostrils  as  affected,  and  by  hearing,  our 
ear  as  affected.  (3)  We  perceive  body  exercising  en- 
ergy. We  do  so  especially  by  the  muscular  sense ;  we 
find  body  resisting  locomotive  energy.  Perhaps  we  have 
some  vague  sense  of  energy  by  all  the  senses  :  the  ob- 
jects perceived  seem  to  affect  us.  But  the  sense  of  power 
is  specially  given  by  our  energy  and  the  resistance  to  our 
energy."*  These  three  cognitions  Dr.  McCosh  calls 
primitive  or  intuitive  cognitions. 

2.  His  doctrine  of  "  First  and  Fundamental  Truths  " 
evinces  the  influence  of  Reid.  Demonstration,  he  says, 
cannot  go  on  forever.  We  cannot  prove  all  things  by 
mediate  evidence.  We  can  show,  however,  that  we 
are  justified  in  making  certain  fundamental  assumptions. 
Of  these  assumptions,  which  he  calls  fundamental  truths, 
the  tests  are  :  self-evidence,  necessity,  and  universality,  f 

Dr.  Porter's  writings^  evince  the  influence  of  German 
speculative  thought,  as  well  as  that  of  Reid  and  his 
School.  However,  the  influence  of  the  Scottish  thinkers 
is  predominant.  As  in  Dr.  McCosh's  philosophy,  this 
may  be  seen  in  his  theory  of  perception  and  primary 
truths. 

i.  His  theory  of  perception  is  intuitive  perception.  The 
object  is  known  immediately.  The  object  thus  known 

*  "  Psychology,"  p.  68. 

f  "Realistic  Philosophy,"  vol.  i,  pp.  33-43.  Cf.  also  "  Intui- 
tions of  the  Mind." 

J  "  The  Human  Intellect,"  New  York,  1875;  «  The  Elements  of 
Intellectual  Science,"  New  York,  1884. 


60  THE  INFLUENCE  OF  REID'S  PHILOSOPHY 

is  "the  sensorium  in  some  form  of  excited  action." 
The  eye,  ear,  nostril,  hand,  etc.,  "with  the  nerves  at- 
tached as  capable  of  the  sentient  function  when  acting 
in  a  living  organism,  are  known  by  the  collective  term, 
the  sensorium,  or  sensory."  This  sensorium  is  known 
immediately  not  only  as  a  non-ego,  but  also  as  extended.* 
Extra-organic  bodies  are  not  known  immediately.  Our 
knowledge  of  them  is  "indirect  or  acquired,  "f  On  this 
latter  point  he  differs  from  Reid  who  holds  to  an  im- 
mediate perception  of  extra-organic  objects. 

2.  We  have  an  intuitive  knowledge  of  first  principles. 
The  criteria  of  such  principles  are:  universality,  necessity 
and  logical  independence  and  originality.  J 

However,  notwithstanding  the  wide  influence  exerted 
by  the  philosophy  of  Reid  in  Great  Britain,  France  and 
America,  his  historical  significance  is  not  great.  Cousin 
regarded  him  as  the  modern  Socrates.  This  estimate  of 
his  historical  position  is  true  in  one  sense.  Being  the 
first  philosopher  to  attempt  to  save  philosophy  from  the 
scepticism  of  Hume,  he  occupies  the  same  position  in 
modern  philosophy  which  Socrates  holds  in  Greek  phi- 
losophy in  his  opposition  to  the  scepticism  of  the  Sophists. 
But  in  his  influence  upon  the  subsequent  development 
of  philosophic  thought,  Reid  cannot  be  compared  with 
Socrates.  To  Kant  must  be  awarded  the  honor  of  such 
a  comparison.  It  was  his  great  work  which  determined 
the  main  course  of  philosophy  subsequent  to  Hume, 
just  as  the  philosophizing  of  Socrates  determined  the 

*  "  Elements  of  Intellectual  Science,"  p.  106. 

f  Ibid.,  p.  155. 

J  Ibid.,  pp.  416-45. 


UPON  SUBSEQUENT  PHILOSOPHIC  THOUGHT.  6l 

course  of  Greek  philosophy,  subsequent  to  the  Sophists. 
Indeed,  as  in  the  philosophy  of  Socrates  we  find  the  best 
standpoint  from  which  to  survey  the  development  of 
ancient  philosophy  from  Thales  to  the  Christian  era,  so 
in  the  philosophy  of  Kant  we  find  the  best  standpoint 
from  which  to  view  the  development  of  modern  philoso- 
phy from  Des  Cartes  to  Von  Hartmann. 

E.  HERSHEY  SNEATH. 


AN  INQUIRY    INTO   THE    HUMAN    MIND    ON 

THE   PRINCIPLES  OF  COMMON  SENSE, 

BY  THOMAS  REID,   D.   D. 


A 


n 


A. 


DEDICATION. 


THE  RIGHT  HONOURABLE   JAMES,   EARL  OF 
FINDLATER  AND  SE AFIELD,  CHANCELLOR 
OF  THE   UNIVERSITY  OF  OLD 
ABERDEEN. 


MY  LORD, — Though  I  apprehend  that  there  are  things, 
new  and  of  some  importance,  in  the  following  Inquiry, 
it  is  not  without  timidity  that  I  have  consented  to  the 
publication  of  it.  The  subject  has  been  canvassed  by 
men  of  very  great  penetration  and  genius:  for  who 
does  not  acknowledge  Des  Cartes,  Malebranche,  Locke, 
Berkeley,  and  Hume,  to  be  such  ?  A  view  of  the  human 
understanding,  so  different  from  that  which  they  have  ex- 
hibited, will,  no  doubt,  be  condemned  by  many,  without 
examination,  as  proceeding  from  temerity  and  vanity. 

But  I  hope  the  candid  and  discerning  Few,  who  are 
capable  of  attending  to  the  operations  of  their  own  minds, 
will  weigh  deliberately  what  is  here  advanced,  before 
they  pass  sentence  upon  it.  To  such  I  appeal,  as  the 
only  competent  judges.  If  they  disapprove,  I  am  prob- 
ably in  the  wrong,  and  shall  be  ready  to  change  my 
opinion  upon  conviction.  If  they  approve,  the  Many 
will  at  last  yield  to  their  authority,  as  they  always  do. 

However  contrary  my  notions  are  to  those  of  the  wri- 
ters I  have  mentioned,  their  speculations  have  been  of 
great  use  to  me,  and  seem  even  to  point  out  the  road 
which  I  have  taken:  and  your  Lordship  knows,  that  the 
merit  of  useful  discoveries  is  sometimes  not  more  justly 

65 


66  THE  PHILOSOPHY  OF  REID. 

due  to  those  that  have  hit  upon  them,  than  to  others  that 
have  ripened  them,  and  brought  them  to  the  birth. 

I  acknowledge,  my  Lord,  that  I  never  thought  of  call- 
ing in  question  the  principles  .commonly  received  with 
regard  to  the  human  understanding,  until  the  "Treatise 
of  Human  Nature  "  was  published  in  the  year  1739.  The 
ingenious  author  of  that  treatise  upon  the  principles  of 
Lo^ke—  wjio  wasjio"sceptic  —  hatrrr3uiTfafsystem  of  scep- 
ticism, which  leaves  no  ground  to  believe"  any  one  thing 
father  than  its  contrary!  His  reasoning  appeare~d  to  me 
to  be  just  ;  there  was,  therefore,  aTliecessiTy  to  call  in 
question  the  principles  upon  which  it  wasToundeTr;  or  to 


But  can  any  ingenuous  mind  admit  this  sceptical  sys- 

tem without  reluctance  ?     I  truly  could  not,   my  Lord  ; 

for  I   am  persuaded,    that   absolute  scepticism   is   not 

more  destructive  of  the  faith  of  a  Christia'n  than  of  the 

science   of  a   philosopher,    and   of  the  prudence  of  a 

man    of    common    understanding.      I    am    persuaded, 

that  the  \my\s\Jiwe_byfaith  as  well  as  the  just;  that, 

I  if  all  belief  could  be  laid  asid~e7  piety,  patrToHsm,  friend- 

\  ship,  parental  affection,  and  private  virtue,  would  appear 

j  as  ridiculous  as  knight-errantry  ;  and  that  the  pursuits 

'  of  pleasure,    of    ambition,    and    of  avarice,   jnust    be 

grounded  upon  belief  as  well  as  those  that  are  honour- 

able or  virtuous. 

*  "This  doctrine  of  ideas"  (says  Dr.  Reid,  in  a  subsequent  work)} 
"  I  once  believed  so  firmly,  as  to  embrace  the  whole  of  Berkeley's 
system  in  consequence  of  it  ;  till,  finding  other  consequences  to  follow 
from  it,  which  gave  me  more  uneasiness  than  the  want  of  a  material 
world,  it  came  into  my  mind,  more  than  forty  years  ago,  to  put  the 
question,  What  evidence  have  I  for  this  doctrine,  that  all  the  objects 
of  my  knowledge  are  ideas  in  my  own  mind  ?  "—  Essays  on  the 
Intellectual  Powers,  Ess.  II.  ch.  x.  p.  162. 

In  like  manner,  Kant  informs  us,  that  it  was  by  Hume's  sceptical 
inferences,  in  regard  to  the  causal  nexus,  that  he  also  **  was  first 
roused  from  his  dogmatic  slumber."  See  the  "  Prolegomena,"  p.  13. 
—  H. 


THE   PHILOSOPHY   OF  REID.  67 

The  day-labourer  toils  at  his  work,  in  the  belief  that  he 
shall  receive  his  wages  at  night ;  and,  if  he  had  not  this 
belief,  he'would  not  toil.  We  may  venture  to  say,  that 
even  the  author  of  this  sceptical  system  wrote  it  in  the 
belief  that  it  should  be  read  and  regarded.  I  hope  he 
wrote  it  in  the  belief  also  that  it  would  be  useful  to  man- 
kind; and,  perhaps,  it  may  prove  so  at  last.  For  I  con- 
ceive the  sceptical  writers  to  be  a  set  of  men  whose  busi- 
ness it  is  to  pick  holes  in  the  fabric  of  knowledge  wher- 
ever it  is  weak  and  faulty ;  and,  when  these  places  are 
properly  repaired,  the  whole  building  becomes  more  firm 
and  solid  than  it  was  formerly. 

For  my  own  satisfaction,  I  entered  into  a  serious  ex- 
amination of  the  principles  upon  which  this  sceptical  sys- 
tem is  built ;  and  was  not  a  little  surprised  to  find,  that 
it  leans  with  its  whole  weight  upon  a  hypothesis,  which 
is  ancient  indeed,  and  hath  been  very  generally  received 
by  philosophers,  but  of  which  I  could  find  no  solid  proof. 
The  hypothesis  I  mean  is,  TrTal  nothing  is  perceived  but 
what  is  in  the_mmd  wnich  perceives  it :  That  we  do  not 
really  perceive  things  that  are  external,  but  only  certain 
images  and  pictures  of  them  impiinted  upon  thlTTmn d, 
which  are  called  impressions  and  ideas. 

If  this  be  true,  supposing  certain  impressions  and  ideas 
to  exist  in  my  mind,  I  cannot,  from  their  existence,  in- 
fer the  existence  of  anything  else :  my  impressions  and 
ideas  are  the  only  existences  of  which  I  can  have  any 
knowledge  or  conception;  and  they  are  such  fleeting  and 
transitory  beings,  that  they  can  have  no  existence  at  all, 
any  longer  than  I  am  conscious  of  them.  So  that,  upon 
this  hypothesis,  the  whole  universe  about  me,  bodies  and 
spirits,  sun,  moon,  stars,  and  earth,  friends  and  relations, 
all  things  without  exception,  which  I  imagined  to  have 
a  permanent  existence,  whether  I  thought  of  them  or  not, 
vanish  at  once  ; 

' '  And,  like  the  baseless  fabric  of  a  vision, 
Leave  not  a  track  behind." 


68  THE  PHILOSOPHY   OF   REID. 

I  thought  it  unreasonable,  my  Lord,  upon  the  author- 
ity of  philosophers,  to  admit  a  hypothesis  which,  in  my 
opinion,  overturns  all  philosophyTall  religion  and  virtue, 
and  all  common"~sense — and,  finding  that  alPthe  sys- 
temsToncerning  theliuman  understanding  which  I  was 
acquainted  with,  were  built  .upon  this  hypothesis,  I  re- 
solved to  inquire  into  this  subject  anew,  without  regard 
to  any Ji^pottiesis. 

^Vhat  I  now  humbly  present  to  your  Lordship,  is  the 
fruit  of  this  inquiry,  so  far  only  as  it  regards  the  five 
senses:  in  which  I  claim  no  other  merit  than  that  of 
having  given  great  attention  to  the  operations  of  my  own 
mind,  and  of  having  expressed,  with  all  the  perspicuity  I 
was  able,  what  I  conceive  every  man,  who  gives  the  same 
attention,  will  feel  and  perceive.  The  productions  of  im- 
agination require  a  genius  which  soars  above  the  com- 
mon rank  ;  but  the  treasures  of  knowledge  are  commonly 
buried  deep,  and  may  be  reached  by  those  drudges  who 
can  dig  with  labour  and  patience,  though  they  have  not 
wings  to  fly.  The  experiments  that  were  to  be  made  in 
this  investigation  suited  me,  as  they  required  no  other 
expense  but  that  of  time  and  attention,  which  I  could 
bestow.  The  leisure  of  an  academical  life,  disengaged 
from  the  pursuits  of  interest  and  ambition ;  the  duty  of  my 
profession,  which  obliged  me  to  give  prelections  on  these 
subjects  to  the  youth ;  and  an  early  inclination  to  specu- 
lations of  this  kind,  have  enabled  me,  as  I  flatter  myself, 
to  give  a  more  minute  attention  to  the  subject  of  this  in- 
quiry, than  has  been  given  before. 

My  thoughts  upon  this  subject  were,  a  good  many  years 
ago,  put  together  in  another  form,  for  the  use  of  my  pu- 
pilf  and  afterwards  were  submitted  to  the  judgment  of  a 
private  philosophical  society,*  of  which  I  have  the  honour 
to  be  a  member,  A  great  part  of  this  Inquiry  was  hon- 
oured even  by  your  Lordship's  perusal.  And  the  en- 

*  Aberdeen  Philosophical  Society  founded  by  Reid  and  Dr.  John 
Gregory. — S. 


THE  PHILOSOPHY   OF  REID.  69 

couragement  which  you,  my  Lord,  and  others,  whose 
friendship  is  my  boast,  and  whose  judgment  I  reverence, 
were  pleased  to  give  me,  counterbalanced  my  timidity  and 
diffidence,  and  determined  me  to  offer  it  to  the  public. 

If  it  appears  to  your  Lordship  to  justify  the  common 
sense  and  reason  of  mankind,  against  the  sceptical  sub- 
tilties  which,  in  this  age,  have  endeavoured  to  put  them 
out  of  countenance — if  it  appears  to  throw  any  new 
light  upon  one  of  the  noblest  parts  of  the  divine  work- 
manship— your  Lordship's  respect  for  the  arts  and  sci- 
ences, and  your  attention  to  everything  which  tends 
to  the  improvement  of  them,  as  well  as  to  everything  else 
that  contributes  to  the  felicity  of  your  country,  leave  me 
no  room  to  doubt  of  your  favourable  acceptance  of  this 
essay,  as  the  fruit  of  my  industry  in  a  profession  where- 
in I  was  accountable  to  your  Lordship ;  and  as  a  testi- 
mony of  the  great  esteem  and  respect  wherewith  I  have 
the  honour  to  be, 

My  Lord,  your  Lordship's  most  obliged  and  most  de- 
voted Servant, 

THO.  REID. 


AN 

• 

INQUIRY   INTO  THE    HUMAN   MIND. 


CHAPTER   I. 

INTRODUCTION. 

Section   /. 

THE    IMPORTANCE    OF   THE    SUBJECT,    AND    THE    MEANS    OF 
PROSECUTING    IT. 

THE  fabric  of  the  human  mind  is  curious  and  won- 
derful, as  well  as  that  of  the  human  body.  The  facul- 
ties of  the  one  are  with  no  less  wisdom  adapted  to  their 
several  ends  than  the  organs  of  the  other.  Nay,  it  is 
reasonable  to  think,  that,  as  the  mind  is  a  nobler  work 
and  of  a  higher  order  than  the  body,  even  more  of  the 
wisdom  and  skill  of  the  divine  Architect  hath  been  em- 
ployed in  its  structure.  It  is,  therefore,  a  subject  highly 
worthy  of  inquiry  on  its  own  account,  but  still  more 
worthy  on  account  of  the  extensive  influence  which  the 
knowledge  of  it  hath  over  every  other  branch  of  science. 

In  the  arts  and  sciences  which  have  least  connection 
with  the  mind,  its  faculties  are  the  engines  which  we 
must  employ;  and  the  better  we  understand  their  nature 
and  use,  their  defects  and  disorders,  the  more  skilfully 
we  shall  apply  them,  and  with  the  greater  success.  But 
in  the  noblest  arts,  the  mind  is  also  the  subject  upon 
which  we  operate.  The  painter,  the  poet,  the  actor,  the 
orator,  the  moralist,  and  the  statesman,  attempt  to  oper- 
70 


SEC.  I.]  THE  PHILOSOPHY   OF  REID.  71 

ate  upon  the  mind  in  different  ways,  and  for  different 
ends;  and  they  succeed  according  as  they  touch  properly 
the  strings  of  the  human  frame.  Nor  can  their  several 
arts  ever  stand  on  a  solid  foundation,  or  rise  to  the 
dignity  of  science,  until  they  are  built  on  the  principles 
of  the  human  constitution. 

Wise  men  now  agree,  or  ought  to  agree,  in  this,  that 
there  is  but  one  way  to  the  knowledge  of  nature's  works 
— the  way  of  observation  and  experiment.  By  our  con- 
stitution, we  have  a  strong  propensity  to  trace  particular 
facts  and  observations  to  general  rules,  and  to  apply 
such  general  rules  to  account  for  other  effects,  or  to  di- 
rect us  in  the  production  of  them.  This  procedure  of 
the  understanding  is  familiar  to  every  human  creature  in 
the  common  affairs  of  life,  and  it  is  the  only  one  by 
which  any  real  discovery  in  philosophy  can  b,e  made. 

The  man  who  first  discovered  that  cold  freezes  water, 
and  that  heat  turns  it  into  vapour,  proceeded  on  the 
same  general  principles,  and  in  the  same  method  by 
which  Newton  discovered  the  law  of  gravitation  and  the 
properties  of  light.  His  regulce  philosophandi  are  maxims 
of  common  sense,  and  are  practised  every  day  in  com- 
mon life;  and  he  who  philosophizes  by  other  rules, 
either  concerning  the  material  system  or  concerning  the 
mind,  mistakes  his  aim. 

Conjectures  and  theories  are  the  creatures  of  men,  and 
will  always  be  found  very  unlike  the  creatures  of  God. 
If  we  would  know  the  works  of  God,  we  must  consult 
themselves  with  attention  and  humility,  without  daring 
to  add  anything  of  ours  to  what  they  declare.     A  just 
interpretation  of  nature  is  the  only  sound  and  orthodox! 
philosophy:  whatever  we  add  of  our  own,  is  apocryphal, 
and  of  no  authority. 

All  our  curious  theories  of  the  formation  of  the  earth, 
of  the  generation  of  animals,  of  the  origin  of  natural  and 
moral  evil,  so  far  as  they  go  beyond  a  just  induction 
from  facts,  are  vanity  and  folly,  no  less  than  the  Vortices 


72  THE  PHILOSOPHY   OF  REID.  ;CH.  I. 

of  Des  Cartes,  or  the  Archaeus  of  Paracelsus.  Perhaps 
the  philosophy  of  the  mind  hath  been  no  less  adulterated 
by  theories,  than  that  of  the  material  system.  The 
theory  of  Ideas  is  indeed  very  ancient,  and  hath  been 
very  universally  received;  but,  as  neither  of  these  titles 
can  give  it  authenticity,  they  ought  not  to  screen  it  from 
a  free  and  candid  examination;  especially  in  this  age, 
when  it  hath  produced  a  system  of  scepticism  that  seems 
to  triumph  over  all  science,  and  even  over  the  dictates  of 
common  sense. 

All  that  we  know  of  the  body,  is  owing  to  anatomical 
dissection  and  observation,  and  it  must  be  by  an  anat- 
omy of  the  mind  that  we  can  discover  its  powers  and 
principles. 

Section  IL 

THE    IMPEDIMENTS    TO    OUR    KNOWLEDGE    OF   THE    MIND. 

But  it  must  be  acknowledged,  that  this  kind  of  anat- 
omy is  much  more  difficult  than  the  other;  and,  there- 
fore, it  needs  not  seem  strange  that  mankind  have  made 
less  progress  in  it.  To  attend  accurately  to  the  opera- 
tions of  our  minds,  and  make  them  an  object  of  thought, 
is  no  easy  matter  even  to  the  contemplative,  and  to  the 
bulk  of  mankind  is  next  to  impossible. 

An  anatomist  who  hath  happy  opportunities,  may  have 
access  to  examine  with  his  own  eyes,  and  with  equal  ac- 
curacy, bodies  of  all  different  ages,  sexes,  and  conditions; 
so  that  what  is  defective,  obscure  or  preternatural  in  one, 
may  be  discerned  clearly  and  in  its  most  perfect  state  in 
another.  But  the  anatomist  of  the  mind  cannot  have 
the  same  advantage.  It  is  his  own  mind  only  that  he 
can  examine  with  any  degree  of  accuracy  and  distinct- 
ness. This  is  the  only  subject  he  can  look  into.  He 
may,  from  outward  signs,  collect  the  operations  of  other 
minds;  but  these  signs  are  for  the  most  part  ambiguous, 
and  must  be  interpreted  by  what  he  perceives  within 
himself. 


SKC.H.]  THE   PHILOSOPHY  OF   REID.  73 

So  that,  if  a  philosopher  could  delineate  to  us,  dis- 
tinctly and  methodically,  all  the  operations  of  the  think- 
ing principle  within  him,  which  no  man  was  ever  able 
to  do,  this  would  be  only  the  anatomy  of  one  particular 
subject;  which  would  be  both  deficient  and  erroneous, 
if  applied  to  human  nature  in  general.  For  a  little  re- 
flection may  satisfy  us,  that  the  difference  of  minds  is 
greater  than  that  of  any  other  beings  which  we  consider 
as  of  the  same  species. 

Of  the  various  powers  and  faculties  we  possess,  there 
are  some  which  nature  seems  both  to  have  planted  and 
reared,  so  as  to  have  left  nothing  to  human  industry. 
Such  are  the  powers  which  we  have  in  common  with  the 
brutes,  and  which  are  necessary  to  the  preservation  of 
the  individual,  or  the  continuance  of  the  kind.  There 
are  other  powers,  of  which  nature  hath  only  planted  the 
seeds  in  our  minds,  but  hath  left  the  rearing  of  them  to 
human  culture.  It  is  by  the  proper  culture  of  these 
that  we  are  capable  of  all  those  improvements  in 
intellectuals,  in  taste,  and  in  morals,  which  exalt  and 
dignify  human  nature;  while,  on  the  other  hand,  the 
neglect  or  perversion  of  them  makes  its  degeneracy  and 
corruption. 

The  two-legged  animal  that  eats  of  nature's  dainties, 
what  his  taste  or  appetite  craves,  and  satisfies  his  thirst  at 
the  crystal  fountain,  who  propagates  his  kind  as  occasion 
and  lust  prompt,  repels  injuries,  and  takes  alternate 
labour  and  repose,  is,  like  a  tree  in  the  forest,  purely  of 
nature's  growth.  But  this  same  savage  hath  within  him 
the  seeds  of  the  logician,  the  man  of  taste  and  breeding, 
the  orator,  the  statesman,  the  man  of  virtue,  and  the 
saint;  which  seeds,  though  planted  in  his  mind  by  na- 
ture, yet,  through  want  of  culture  and  exercise,  must  lie 
for  ever  buried,  and  be  hardly  perceivable  by  himself  or 
by  others. 

The  lowest  degree  of  social  life  will  bring  to  light 
some  of  those  principles  which  lay  hid  in  the  savage  state; 


74  THE  PHILOSOPHY  OF  REID.  [Cn.  I. 

and,  according  to  his  training,  and  company,  and  man- 
ner of  life,  some  of  them,  either  by  their  native  vigor,  or 
by  the  force  of  culture,  will  thrive  and  grow  up  to  great 
perfection,  others  will  be  strangely  perverted  from  their 
natural  form,  and  others  checked,  or  perhaps  quite 
eradicated. 

This  makes  human  nature  so  various  and  multiform 
in  the  individuals  that  partake  of  it,  that,  in  point  of 
morals  and  intellectual  endowments,  it  fills  up  all  that 
gap  which  we  conceive  to  be  between  brutes  and  devils 
below,  and  the  celestial  orders  above;  and  such  a  pro- 
digious diversity  of  minds  must  make  it  extremely  diffi- 
cult to  discover  the  common  principles  of  the  species. 

The  language  of  philosophers,  with  regard  to  the 
original  faculties  of  the  mind,  is  so  adapted  to  the  pre- 
vailing system,  that  it  cannot  fit  any  other;  like  a  coat 
that  fits  the  man  for  whom  it  was  made,  and  shews  him 
to  advantage,  which  yet  will  sit  very  awkward  upon  one 
of  a  different  make,  although  perhaps  as  handsome  and 
as  well  proportioned.  It  is  hardly  possible  to  make  any 
innovation  in  our  philosophy  concerning  the  mind  and 
its  operations,  without  using  new  words  and  phrases,  or 
giving  a  different  meaning  to  those  that  are  received — a 
liberty  which,  even  when  necessary,  creates  prejudice 
and  misconstruction,  and  which  must  wait  the  sanction 
of  time  to  authorize  it;  for  innovations  in  language,  like 
those  in  religion  and  government,  are  always  suspected 
and  disliked  by  the  many,  till  use  hath  made  them  famil- 
iar, and  prescription  hath  given  them  a  title. 

If  the  original  perceptions  and  notions  of  the  mind 
were  to  make  their  appearance  single  and  unmixed,  as 
we  first  received  them  from  the  hand  of  nature,  one  ac- 
customed to  reflection  would  have  less  difficulty  in  tracing 
them;  but  before  we  are  capable  of  reflection,  they  are  so 
mixed,  compounded,  and  decompounded,  by  habits,  as- 
sociations, and  abstractions,  that  it  is  hard  to  know  what 
they  were  originally.  The  mind  may,  in  this  respect, 


SEC.  II.]  THE  PHILOSOPHY  OF  REID,  75 

be  compared  to  an  apothecary  or  a  chemist,  whose 
materials  indeed  are  furnished  by  nature;  but,  for  the 
purposes  of  his  art,  he  mixes,  compounds,  dissolves, 
evaporates,  and  sublimes  them,  till  they  put  on  a  quite 
different  appearance;  so  that -it  is  very  difficult  to  know 
what  they  were  at  first,  and  much  more  to  bring  them 
back  to  their  original  and  natural  form.  And  this  work 
of  the  mind  is  not  carried  on  by  deliberate  acts  of  mature 
reason,  which  we  might  recollect,  but  by  means  of  in- 
stincts, habits,  associations,  and  other  principles,  which 
operate  before  we  come  to  the  use  of  reason;  so  that  it  is 
extremely  difficult  for  the  mind  to  return  upon  its  own 
footsteps,  and  trace  back  those  operations  which  have 
employed  it  since  it  first  began  to  think  and  to  act. 

Could  we  obtain  a  distinct  and  full  history  of  all  that 
hath  past  in  the  mind  of  a  child,  from  the  beginning  of 
life  and  sensation,  till  it  grows  up  to  the  use  of  reason — 
how  its  infant  faculties  began  to  work,  and  how  they 
brought  forth  and  ripened  all  the  various  notions, 
opinions  and  sentiments  which  we  find  in  ourselves 
when  we  come  to  be  capable  of  reflection — this  would  be 
a  treasure  of  natural  history,  which  would  probably  give 
more  light  into  the  human  faculties,  than  all  the  systems 
of  philosophers  about  them  since  the  beginning  of  the 
world.  But  it  is  in  vain  to  wish  for  what  nature  has  not 
put  within  the  reach  of  our  power.  Reflection,  the  only 
instrument  by  which  we  can  discern  the  powers  of  the 
mind,  comes  too  late  to  observe  the  progress  of  nature, 
in  raising  them  from  their  infancy  to  perfection. 

It  must  therefore  require  great  caution,  and  great 
application  of  mind,  for.a  man  that  is  grown  up  in  all 
the  prejudices  of  education,  fashion,  and  philosophy,  to 
unravel  his  notions  and  opinions,  till  he  find  out  the 
simple  and  original  principles  of  his  constitution,  of 
which  no  account  can  be  given  but  the  will  of  our 
Maker.  This  may  be  truly  called  an  analysis  of  the 
human  faculties;  and,  till  this  is  performed,  it  is  in  vain 


76  THE  PHILOSOPHY   OF   REID.  [CH.  I. 

we  expect  any  just  system  of  the  mind— that  is,  an 
enumeration  of  the  original  powers  and  laws  of  our  con- 
stitution, and  an  explication  from  them  of  the  various 
phenomena  of  human  nature. 

Success  in  an  inquiry  of  this  kind,  it  is  not  in  human 
power  to  command  ;  but,  perhaps,  it  is  possible,  by 
caution  and  humility,  to  avoid  error  and  delusion.  The 
labyrinth  may  be  too  intricate,  and  the  thread  too  fine, 
to  be  traced  through  all  its  windings;  but,  if  we  stop 
where  we  can  trace  it  no  farther,  and  secure  the  ground 
we  have  gained,  there  is  no  harm  done;  a  quicker  eye  may 
in  time  trace  it  farther. 

It  is  genius,  and  not  the  want  of  it,  that  adulterates 
philosophy,  and  fills  it  with  error  and  false  theory.  A 
v  creative  imagination  disdains  the  mean  offices  of  dig- 
ging for  a  foundation,  of  removing  rubbish,  and  carry- 
ing materials;  leaving  these  servile  employments  to  the 
drudges  in  science,  it  plans  a  design,  and  raises  a  fabric. 
.  Invention  supplies  materials  where  they  are  wanting,  and 
fancy  adds  colouring  and  every  befitting  ornament.  The 
work  pleases  the  eye,  and  wants  nothing  but  solidity  and 
a  good  foundation.  It  seems  even  to  vie  with  the  works 
of  nature,  till  some  succeeding  architect  blows  it  into 
rubbish,  and  builds  as  goodly  a  fabric  of  his  own  in  its 
place.  Happily  for  the  present  age,  the  castle-builders 
employ  themselves  more  in  romance  than  in  philosophy. 
That  is  undoubtedly  their  province,  and  in  those  regions 
the  offspring  of  fancy  is  legitimate,  but  in  philosophy  it 
is  all  spurious. 

Section  III. 

THE  PRESENT  STATE  OF  THIS  PART  OF  PHILOSOPHY OF  DES 

CARTES,  MALEBRANCHE,  AND  LOCKE. 

That  our  philosophy  concerning  the  mind  and  its 
faculties  is  but  in  a  very  low  state,  may  be  reasonably 
conjectured  even  by  those  who  never  have  narrowly  ex- 


SEC.  III.]  THE  PHILOSOPHY  OF  REID.  77 

amined  it.  Are  there  any  principles,  with  regard  to  the 
mind,  settled  with  that  perspicuity  and  evidence  which 
attends  the  principles  of  mechanics,  astronomy  and 
optics  ?  These  are  really  sciences  built  upon  laws  of 
nature  which  universally  obtain.  What  is  discovered  in 
them  is  no  longer  matter  of  dispute:  future  ages  may 
add  to  it ;  but,  till  the  course  of  nature  be  changed, 
what  is  already  established  can  never  be  overturned.  But 
when  we  turn  our  attention  inward,  and  consider  the 
phaenomena  of  human  thoughts,  opinions,  and  percep- 
tions, and  endeavour  to  trace  them  to  the  general  laws 
and  the  first  principles  of  our  constitution,  we  are  im- 
mediately involved  in  darkness  and  perplexity;  and, 
if  common  sense,  or  the  principles  of  education,  hap- 
pen not  to  be  stubborn,  it  is  odds  but  we  end  in  absolute 
scepticism. 

Des  Cartes,  finding  nothing  established  in  this  part  of 
philosophy,  in  order  to  lay  the  foundation  of  it  deep, 
resolved  not  to  believe  his  own  existence  till  he  should 
be  able  to  give  a  good  reason  for  it.  He  was,  perhaps, 
the  first  that  took  up  such  a  resolution;  but,  if  he  could 
indeed  have  effected  his  purpose,  and  really  become 
diffident  of  his  existence,  his  case  would  have  been  de- 
plorable, and  without  any  remedy  from  reason  or  philos- 
ophy. A  man  that  disbelieves  his  own  existence,  is 
surely  as  unfit  to  be  reasoned  with  as  a  man  that  believes 
he  is  made  of  glass.  There  may  be  disorders  in  the 
human  frame  that  may  produce  such  extravagancies,  but 
they  will  never  be  cured  by  reasoning.  Des  Cartes,  in- 
deed, would  make  us  believe  that  he  got  out  of  this 
delirium  by  this  logical  argument,  Cogito,  ergo  sum;  but 
it  is  evident  he  was  in  his  senses  all  the  time,  and  never 
seriously  doubted  of  his  existence;  for  he  takes  it  for 
granted  in  this  argument,  and  proves  nothing  at  all.  I 
am  thinking,  says  he — therefore,  I  am.  And  is  it  not 
as  good  reasoning  to  say,  I  am  sleeping — therefore,  I 
am  ?  or,  I  am  doing  nothing — therefore,  I  am  ?  If  a 


78  THE  PHILOSOPHY  OF  REID.  [Cn.  I. 

body  moves,  it  must  exist,  no  doubt;  but,  if  it  is  at  rest 
it  must  exist  likewise.* 

Perhaps  Des  Cartes  meant  not  to  assume  his  own  ex- 
istence in  this  enthymeme,  but  the  existence  of  thought; 
and  to  infer  from  that  the  existence  of  a  mind,  or  subject 
of  thought.  But  why  did  he  not  prove  the  existence  of 
his  thought  ?  Consciousness,  it  may  be  said,  vouches 
that.  But  who  is  voucher  for  consciousness  ?  Can  any 
man  prove  that  his  consciousness  may  not  deceive  him  ? 
No  man  can;  nor  can  we  give  a  better  reason  for  trusting 
to  it,  than  that  every  man,  while  his  mind  is  sound,  is 
determined,  by  the  constitution  of  his  nature,  to  give 
implicit  belief  to  it,  and  to  laugh  at  or  pity  the  man  who 
doubts  its  testimony.  And  is  not  every  man,  in  his  wits, 
as  much  determined  to  take  his  existence  upon  trust  as 
his  consciousness  ? 

The  other  proposition  assumed  in  this  argument, 
That  thought  cannot  be  without  a  mind  or  subject,  is 
liable  to  the  same  objection:  not  that  it  wants  evidence 
but  that  its  evidence  is  no  clearer,  nor  more  immediate, 
than  that  of  the  proposition  to  be  proved  by  it.  And, 
taking  all  these  propositions  together — I  think;  I  am 
conscious;  Everything  that  thinks,  exists;  I  exist — would 
not  every  sober  man  form  the  same  opinion  of  the  man 
who  seriously  doubted  any  one  of  them  ?  And  if  he  was 
his  friend,  would  he  not  hope  for  his  cure  from  physic 
and  good  regimen,  rather  than  from  metaphysic  and 
logic  ? 

But  supposing  it  proved,  that  my  thought  and  my 
consciousness  must  have  a  subject,  and  consequently  that 
I  exist,  how  do  I  know  that  all  that  train  and  succession 
of  thoughts  which  I  remember  belong  to  one  subject, 
and  that  the  I  of  this  moment  is  the  very  individual  I  of 
yesterday  and  of  times  past  ? 

*  The  nature  ot  the  Cartesian  Doubt  and  its  solution  is  here  mis- 
apprehended.— II.  See  note,  I.  P.,  Essay  ii.,  ch.  8. 


SEC.  III.]  THE  PHILOSOPHY  OF  REID.  79 

Des  Cartes  did  not  think  proper  to  start  this  doubt ; 
but  Locke  has  done  it ;  and,  in  order  to  resolve  it, 
gravely  determines  that  personal  identity  consists  in 
consciousness — that  is,  if  you  are  conscious  that  you  did 
such  a  thing  a  twelvemonth  ago,  this  consciousness  makes 
you  to  be  the  very  person  that  did  it.  Now  conscious- 
ness of  what  is  past  can  signify  nothing  else  but  the  re- 
membrance that  I  did  it ;  so  that  Locke's  principle  must 
be,  That  identity  consists  in  remembrance ;  and,  conse- 
quently, a  man  must  lose  his  personal  identity  with  re- 
gard to  everything  he  forgets. 

Nor  are  these  the  only  instances  whereby  our  philos- 
ophy concerning  the  mind  appears  to  be  very  fruitful  in 
creating  doubts,  but  very  unhappy  in  resolving  them. 

Des  Cartes,  Malebranche,  and  Locke,  have  all  em- 
ployed their  genius  and  skill  to  prove  the  existence  of 
a  material  world  :  and  with  very  bad  success.  Poor 
untaught  mortals  believe  undoubtedly  that  there  is  a 
sun,  moon,  and  stars  ;  an  earth,  which  we  inhabit ; 
country,  friends,  and  relations,  which  we  enjoy ;  land, 
houses,  and  movables,  which  we  possess.  But  philos- 
ophers, pitying  the  credulity  of  the  vulgar,  resolve  to 
have  no  faith  but  what  is  founded  upon  reason.*  They 
apply  to  philosophy  to  furnish  them  with  reasons  for  the 
belief  of  those  things  which  all  mankind  have  believed, 
without  being  able  to  give  any  reason  for  it.  And  surely 
one  would  expect,  that,  in  matters  of  such  importance, 
the  proof  would  not  be  difficult :  but  it  is  the  most  dif- 
ficult  thing  in  the  world.  For  these  three  great  men, 
with  the  best  good  will,  have  not  been  able,  from  all  the 
treasures  of  philosophy,  to  draw  one  argument  that  is  fit 
to  convince  a  man  that  can  reason,  of  the  existence  of 
any  one  thing  without  him.  Admired  Philosophy! 

*  Reason  is  here  employed,  by  Reid,  not  as  a  synonyme  for  Com- 
mon Sense,  (yov£,  locus  principiorum)  and  as  he  himself  more  cor- 
rectly employs  it  in  his  later  works,  but  as  equivalent  to  Reasoning, 
(dictvoia,  discursus  mentalis.)  See  Note  A. — H. 


8o  THE  PHILOSOPHY  OF  REID.  [CH.  I. 

daughter  of  light  !  parent  of  wisdom  and  knowledge  ! 
if  thou  art  she,  surely  thou  hast  not  yet  arisen  upon  the 
human  mind,  nor  blessed  us  with  more  of  thy  rays  than 
are  sufficient  to  shed  a  darkness  visible  upon  the  human 
faculties,  and  to  disturb  that  repose  and  security  which 
happier  mortals  enjoy,  who  never  approached  thine 
altar,  nor  felt  thine  influence  !  But  if,  indeed,  thou  hast 
not  power  to  dispel  those  clouds  and  phantoms  which 
thou  hast  discovered  or  created,  withdraw  this  penurious 
and  malignant  ray;  I  despise  Philosophy,  and  renounce 
its  guidance — let  my  soul  dwell  with  Common  Sense.* 

Section  IV. 

APOLOGY  FOR   THOSE    PHILOSOPHERS. 

But,  instead  of  despising  the  dawn  of  light,  we  ought 
rather  to  hope  for  its  increase  :  instead  of  blaming  the 
philosophers  I  have  mentioned  for  the  defects  and  blem- 
ishes of  their  system  we  ought  rather  to  honour  their  mem- 
ories, as  the  first  discoverers  of  a  region  in  philosophy 
formerly  unknown  ;  and  however  lame  and  imperfect  the 
system  may  be,  they  have  opened  the  way  to  future  dis- 
coveries, and  are  justly  entitled  to  a  great  share  in  the 
merit  of  them.  They  have  removed  an  infinite  deal  of 
dust  and  rubbish,  collected  in  the  ages  of  scholastic  soph- 
istry, which  had  obstructed  the  way.  They  have  put 
us  in  the  right  road — that  of  experience  and  accurate  re- 
flection. They  have  taught  us  to  avoid  the  snares  of  am- 
biguous and  ill-defined  words,  and  have  spoken  and 
thought  upon  this  subject  with  a  distinctness  and  perspi- 
cuity formerly  unknown.  They  have  made  many  open- 
ings that  may  lead  to  the  discovery  of  truths  which  they 
did  not  reach,  or  to  the  detection  of  errors  in  which  they 
were  involuntarily  entangled. 

*  Mr.  Stewart  very  justly  censures  the  vagueness  and  ambiguity 
of  this  passage.  Elem,  vol  ii.,  ch.  i.,  §  3,  p.  92,  8vo  editions. — H- 


SBC.V.]  THE  PHILOSOPHY  OF  REID.  8l 

It  may  be  observed,  that  the  defects  and  blemishes  in 
the  received  philosophy  concerning  the  mind,  which  have 
most  exposed  it  to  the  contempt  and  ridicule  of  sensible 
men,  have  chiefly  been  owing  to  this — that  the  votaries 
of  this  Philosophy,  from  a  natural  prejudice  in  her  fa- 
vour, have  endeavoured  to  extend  her  jurisdiction  beyond 
its  just  limits,  and  to  call  to  her  bar  the  dictates  of  Com- 
mon Sense.  But  these  decline  this  jurisdiction  ;  they  dis- 
dain the  trial  of  reasoning,  and  disown  its  authority;  they 
neither  claim  its  aid,  nor  dread  its  attacks. 

In  this  unequal  contest  betwixt  Common  Sense  and 
Philosophy,  the  latter  will  always  come  off  both  with 
dishonour  and  loss;  nor  can  she  ever  thrive  till  this  rival- 
ship  is  dropt,  these  encroachments  given  up,  and  a 
cordial  friendship  restored:  for,  in  reality,  Common 
Sense  holds  nothing  of  Philosophy,  nor  needs  her  aid. 
But,  on  the  other  hand,  Philosophy  (if  I  may  be  per- 
mitted to  change  the  metaphor)  has  no  other  root  but 
the  principles  of  Common  Sense  ;  it  grows  out  of  them, 
and  draws  its  nourishment  from  them.  Severed  from  this 
root,  its  honours  wither,  its  sap  is  dried  up,  it  dies  and  rots. 

The  philosophers  of  the  last  age,  whom  I  have  men- 
tioned, did  not  attend  to  the  preserving  this  union  and 
subordination  so  carefully  as  the  honour  and  interest  of 
philosophy  required:  but  those  of  the  present  have  waged 
open  war  with  Common  Sense,  and  hope  to  make  a 
complete  conquest  of  it  by  the  subtilties  of  Philosophy — 
an  attempt  no  less  audacious  and  vain  than  that  of  the 
giants  to  dethrone  almighty  Jove. 

Section   V. 

OF     BISHOP     BERKELEY THE     "TREATISE     OF     HUMAN     NA- 
TURE"  AND    OF    SCEPTICISM. 

The  present  age,  I  apprehend,  has  not  produced  two 
more  acute  or  more  practised  in  this  part  of  philosophy, 


82  THE  PHILOSOPHY   OF   REID.  [Cii.  I. 

than  the  Bishop  of  Cloyne,  and  the  author  of  the 
"  Treatise  of  Human  Nature."  The  first  was  no  friend 
to  scepticism,  but  had  that  warm  concern  for  religious 
and  moral  principles  which  became  his  order  :  yet  the 
result  of  his  inquiry  was  a  serious  conviction  that  there 
is  no  such  thing  as  a  material  world — nothing  in  nature 
but  spirits  and  ideas;  and  that  the  belief  of  material  sub- 
stances, and  of  abstract  ideas,  are  the  chief  causes  of  all 
our  errors  in  philosophy,  and  of  all  infidelity  and  heresy 
in  religion.  His  arguments  are  founded  upon  the 
principles  which  were  formerly  laid  down  by  Des  Cartes, 
Malebranche,  and  Locke,  and  which  have  been  very 
generally  received. 

And  the  opinion  of  the  ablest  judges  seems  to  be,  that 
they  neither  have  been,  nor  can  be  confuted;  and  that  he 
hath  proved  by  unanswerable  arguments  what  no  man 
in  his  senses  can  believe. 

The  second  proceeds  upon  the  same  principles,  but 
carries  them  to  their  full  length;  and,  as  the  Bishop  un- 
did the  whole  material  world,  this  author,  upon  the  same 
grounds,  undoes  the  world  of  spirits,  and  leaves  nothing 
in  nature  but  ideas  and  impressions,  without  any  sub- 
ject on  which  they  may  be  impressed. 

It  seems  to  be  a  peculiar  strain  of  humour  in  this 
author,  to  set  out  in  his  introduction  by  promising,  with 
a  grave  face,  no  less  than  a  complete  system  of  the 
sciences,  upon  a  foundation  entirely  new — to  wit,  that 
of  human  nature — when  the  intention  of  the  whole  work 
is  to  shew,  that  there  is  neither  human  nature  nor  science 
in  the  world.  It  may  perhaps  be  unreasonable  to  com- 
plain of  this  conduct  in  an  author  who  neither  believes  his 
own  existence  nor  that  of  his  reader;  and  therefore  could 
not  mean  to  disappoint  him,  or  to  laugh  at  his  credulity. 
Vet  I  cannot  imagine  that  the  author  of  the  ' '  Treatise 
of  Human  Nature "  is  so  sceptical  as  to  plead  this 
apology.  He  believed,  against  his  principles,  that  he 
should  be  read,  and  that  he  should  retain  his  personal 


SEC.  V.]  THE  PHILOSOPHY   OF  REID.  83 

identity,  till  he  reaped  the  honour  and  reputation  justly 
due  to  his  metaphysical  acumen.  Indeed,  he  ingeniously 
acknowledges,  that  it  was  only  in  solitude  and  retirement 
that  he  could  yield  any  assent  to  his  own  philosophy; 
society,  like  daylight,  dispelled  the  darkness  and  fogs 
of  scepticism,  and  made  him  yield  to  the  dominion  of 
common  sense.  Nor  did  I  ever  hear  him  charged  with 
doing  anything,  even  in  solitude,  that  argued  such  a  de- 
gree of  scepticism  as  his  principles  maintain.  Surely  if 
his  friends  apprehended  this,  they  would  have  the  charity 
never  to  leave  him  alone. 

Pyrrho  the  Elean,  the  father  of  this  philosophy, 
seems  to  have  carried  it  to  greater  perfection  than  any  of 
his  successors :  for,  if  we  may  believe  Antigonus  the 
Carystian,  quoted  by  Diogenes  Laertius,  his  life  cor- 
responded to  his  doctrine.  And,  therefore,  if  a  cart  run 
against  him,  or  a  dog  attacked  him,  or  if  he  came  upon 
a  precipice,  he  would  not  stir  a  foot  to  avoid  the  danger, 
giving  no  credit  to  his  senses.  But  his  attendants,  who, 
happily  for  him,  were  not  so  great  sceptics,  took  care 
to  keep  him  out  of  harm's  way;  so  that  he  lived  till  he 
was  ninety  years  of  age.  Nor  is  it  to  be  doubted  but 
this  author's  friends  would  have  been  equally  careful  to 
keep  him  from  harm,  if  ever  his  principles  had  taken  too 
strong  a  hold  of  him. 

It  is  probable  the  "Treatise  of  Human  Nature"  was 
not  written  in  company;  yet  it  contains  manifest  indica- 
tions that  the  author  every  now  and  then  relapsed  into 
the  faith  of  the  vulgar,  and  could  hardly,  for  half  a  dozen 
pages,  keep  up  the  sceptical  character. 

In  like  manner,  the  great  Pyrrho  himself  forgot  his 
principles  on  some  occasions;  and  is  said  once  to  have 
been  in  such  a  passion  with  his  cook,  who  probably  had 
not  roasted  his  dinner  to  his  mind,  that  with  the  spit  in 
his  hand,  and  the  meat  upon  it,  he  pursued  him  even 
into  the  market-place. 

It  is  a  bold  philosophy  that  rejects,  without  ceremony, 


84  THE  PHILOSOPHY  OF  REID.  [Cn.  I. 

principles  which  irresistibly  govern  the  belief  and  the 
conduct  of  all  mankind  in  the  common  concerns  of  life; 
and  to  which  the  philosopher  himself  must  yield,  after 
he  imagines  he  hath  confuted  them.  Such  principles  are 
older,  and  of  more  authority,  than  Philosophy:  she  rests 
upon  them  as  her  basis,  not  they  upon  her.  If  she  could 
overturn  them,  she  must  be  buried  in  their  ruins;  but  all 
the  engines  of  philosophical  subtil  ty  are  too  weak  for 
this  purpose;  and  the  attempt  is  no  less  ridiculous  than 
if  a  mechanic  should  contrive  an  axis  in  peritrochio  to 
remove  the  earth  out  of  its  place;  or  if  a  mathematician 
should  pretend  to  demonstrate  that  things  equal  to  the 
same  thing  are  not  equal  to  one  another. 

Zeno  endeavoured  to  demonstrate  the  impossibility  of 
motion;  Hobbes,  that  there  was  no  difference  between 
right  and  wrong;  and  this  author,  that  no  credit  is  to  be 
given  to  our  senses,  to  our  memory,  or  even  to  demon- 
stration. Such  philosophy  is  justly  ridiculous,  even  to 
those  who  cannot  detect  the  fallacy  of  it.  It  can  have 
no  other  tendency,  than  to  shew  the  acuteness  of  the  so- 
phist, at  the  expense  of  disgracing  reason  and  human 
nature,  and  making  mankind  Yahoos. 


Section   VI. 
OF  THE  "TREATISE  OF  HUMAN  NATURE." 

There  are  other  prejudices  against  this  system  of  hu- 
man nature,  which,  even  upon  a  general  view,  may 
make  one  diffident  of  it. 

Des  Cartes,  Hobbes,  and  this  author,  have  each  of 
them  given  us  a  system  of  human  nature;  an  undertak- 
ing too  vast  for  any  one  man,  how  great  soever  his  ge- 
nius and  abilities  may  be.  There  must  surely  be  reason 
to  apprehend,  that  many  parts  of  human  nature  never 
came  under  their  observation;  and  that  others  have  been 
stretched  and  distorted,  to  fill  up  blanks,  and  complete 


SEC.  VI.]  THE  PHILOSOPHY   OF   REID.  85 

the  system.  Christopher  Columbus,  or  Sebastian  Cabot, 
might  almost  as  reasonably  have  undertaken  to  give  us  a 
complete  map  of  America. 

There  is  a  certain  character  and  style  in  Nature's 
works,  which  is  never  attained  in  the  most  perfect  imi- 
tation of  them.  This  seems  to  be  wanting  in  the  systems 
of  human  nature  I  have  mentioned,  and  particularly  in 
the  last.  One  may  see  a  puppet  make  variety  of  motions 
and  gesticulations,  which  strike  much  at  first  view  ;  but 
when  it  is  accurately  observed,  and  taken  to  pieces,  our 
admiration  ceases:  we  comprehend  the  whole  art  of  the 
maker.  How  unlike  is  it  to  that  which  it  represents  ! 
What  a  poor  piece  of  work  compared  with  the  body  of  a 
man,  whose  structure  the  more  we  know,  the  more  won- 
ders we  discover  in  it,  and  the  more  sensible  we  are  of 
our  ignorance  !  Is  the  mechanism  of  the  mind  so  easily 
comprehended,  when  that  of  the  body  is  so  difficult  ? 
Yet,  by  this  system,  three  laws  of  association,  joined  to 
a  few  original  feelings,  explain  the  whole  mechanism  of 
sense,  imagination,  memory,  belief,  and  of  all  the  actions, 
and  passions  of  the  mind.  Is  this  the  man  that  Na- 
ture made  ?  I  suspect  it  is  not  so  easy  to  look  behind 
the  scenes  in  Nature's  work.  This  is  a  puppet,  surely, 
contrived  by  too  bold  an  apprentice  of  Nature,  to  mimic 
her  work.  It  shews  tolerably  by  candle-light ;  but, 
brought  into  clear  day,  and  taken  to  pieces,  it  will  ap- 
pear to  be  a  man  made  with  mortar  and  a  trowel.  The 
more  we  know  of  other  parts  of  nature,  the  more  we 
like  and  approve  them.  The  little  I  know  of  the  planet- 
ary system,  of  the  earth,  which  we  inhabit ;  of  minerals, 
vegetables,  and  animals  ;  of  my  own  body  ;  and  of  the 
laws  which  obtain  in  these  parts  of  nature — opens  to  my 
mind  grand  and  beautiful  scenes,  and  contributes  equally 
to  my  happiness  and  power.  But,  when  I  look  within, 
and  consider  the  mind  itself,  which  makes  me  capable 
of  all  these  prospects  and  enjoyments — if  it  is,  indeed, 
what  the  "  Treatise  of  Human  Nature"  makes  it — I  find 


86  THE  PHILOSOPHY   OF  REID.  [Cn.  I. 

I  have  been  only  in  an  enchanted  castle,  imposed  upon 
by  spectres  and  apparitions.  I  blush  inwardly  to  think 
how  I  have  been  deluded  ;  I  am  ashamed  of  my  frame, 
and  can  hardly  forbear  expostulating  with  my  destiny. 
Is  this  thy  pastime,  O  Nature,  to  put  such  tricks  upon  a 
silly  creature,  and  then  to  -take  off  the  mask,  and  shew 
him  how  he  hath  been  befooled  ?  If  this  is  the  philo- 
sophy of  human  nature,  my  soul,  enter  thou  not  into  her 
secrets  !  It  is  surely  the  forbidden  tree  of  knowledge  ; 
I  no  sooner  taste  of  it,  than  I  perceive  myself  naked, 
and  stript  of  all  things — yea,  even  of  my  very  self.  I  see 
myself,  and  the  whole  frame  of  nature,  shrink  into  fleet- 
ing ideas,  which,  like  Epicurus's  atoms,  dance  about  in 
emptiness. 

Section  VIL 

THE     SYSTEM     OF     ALL   THESE    AUTHORS    IS    THE    SAME,    AND 
LEADS  TO  SCEPTICISM. 

But  what  if  these  profound  disquisitions  into  the  first 
principles  of  human  nature,  do  naturally  and  necessarily 
plunge  a  man  into  this  abyss  of  scepticism  ?  May  we  not 
reasonably  judge  so  from  what  hath  happened  ?  Des 
Cartes  no  sooner  began  to  dig  in  this  mine,  than  scepti- 
cism was  ready  to  break  in  upon  him.  He  did  what  he 
could  to  shut  it  out.  Malebranche  and  Locke,  who  dug 
deeper,  found  the  difficulty  of  keeping  out  this  enemy 
still  to  increase;  but  they  laboured  honestly  in  the  design. 
Then  Berkeley,  who  carried  on  the  work,  despairing  of 
securing  all,  bethought  himself  of  an  expedient: — By 
giving  up  the  material  world,  which  he  thought  might 
be  spared  without  loss,  and  even  with  advantage,  he 
hoped,  by  an  impregnable  partition,  to  secure  the  world 
of  spirits.  But  alas  !  the  "Treatise  of  Human  Nature" 
wantonly  sapped  the  foundation  of  this  partition,  and 
drowned  all  in  one  universal  deluge. 

These  facts,   which  are   undeniable,  do,  indeed,  give 


SEC.  VIII.]  THE   PHILOSOPHY   OF   REID.  8? 

reason  to  apprehend  that  Des  Cartes'  system  of  the  hu- 
man understanding,  which  I  shall  beg  leave  to  call  the  ideal 
system,  and  which,  with  some  improvements  made  by  la- 
ter writers,  is  now  generally  received,  hath  some  original 
defect;  that  this  scepticism  is  inlaid  in  it,  and  reared 
along  with  it :  and,  therefore,  that  we  must  lay  it  open 
to  the  foundation,  and  examine  the  materials,  before  we 
can  expect  to  raise  any  solid  and  useful  fabric  of  know- 
ledge on  this  subject. 


Section  VIII. 

WE  OUGHT  NOT  TO  DESPAIR  OF  A  BETTER. 

But  is  this  to  be  despaired  of,  because  Des  Cartes  and 
his  followers  have  failed  ?  By  no  means.  This  pusilla- 
nimity would  be  injurious  to  ourselves  and  injurious  to 
truth.  Useful  discoveries  are  sometimes  indeed  the  effect 
of  superior  genius,  but  more  frequently  they  are  the  birth  of 
time  and  of  accidents.  A  traveller  of  good  judgment 
may  mistake  his  way,  and  be  unawares  led  into  a  wrong 
track;  and  while  the  road  is  fair  before  him,  he  may  go 
on  without  suspicion  and  be  followed  by  others;  but, 
when  it  ends  in  a  coal-pit,  it  requires  no  great  judgment 
to  know  that  he  hath  gone  wrong,  nor  perhaps  to  find 
out  what  misled  him. 

In  the  meantime,  the  unprosperous  state  of  this  part 
of  philosophy  hath  produced  an  effect,  somewhat  dis- 
couraging indeed  to  any  attempt  of  this  nature,  but  an 
effect  which  might  be  expected,  and  which  time  only 
and  better  success  can  remedy.  Sensible  men,  who 
never  will  be  sceptics  in  matters  of  common  life,  are  apt 
to  treat  with  sovereign  contempt  everything  that  hath 
been  said,  or  is  to  be  said,  upon  this  subject.  It  is  meta- 
physic,  say  they  :  who  minds  it  ?  Let  scholastic  sophis- 
ters  entangle  themselves  in  their  own  cobwebs  ;  I  am  re- 


88  THE  PHILOSOPHY  OF  REID.         [CH.  I..  SEC.  VIII. 

solved  to  take  my  own  existence,  and  the  existence  of 
other  things,  upon  trust ;  and  to  believe  that  snow  is  cold, 
and  honey  sweet,  whatever  they  may  say  to  the  contrary. 
He  must  either  be  a  fool,  or  want  to  make  a  fool  of  me, 
that  would  reason  me  out  of  my  reason  and  senses. 

I  confess  I  know  not  what  a  sceptic  can  answer  to  this, 
nor  by  what  good  argument  he  can  plead  even  for  a  hear- 
ing ;  for  either  his  reasoning  is  sophistry,  and  so  deserves 
contempt ;  or  there  is  no  truth  in  human  faculties — and 
then  why  should  we  reason  ? 

If,  therefore,  a  man  find  himself  intangled  in  these  meta- 
physical toils,  and  can  find  no  other  way  to  escape,  let 
him  bravely  cut  the  knot  which  he  cannot  loose,  curse 
metaphysic,  and  dissuade  every  man  from  meddling  with 
it ;  for,  if  I  have  been  led  into  bogs  and  quagmires  by 
following  an  ignis  fatuus,  what  can  I  do  better  than  to 
warn  others  to  beware  of  it?  If  philosophy  contradicts 
herself,  befools  her  votaries,  and  deprives  them  of  every 
object  worthy  to  be  pursued  or  enjoyed,  let  her  be  sent 
back  to  the  infernal  regions  from  which  she  must  have 
had  her  original. 

But  is  it  absolutely  certain  that  this  fair  lady  is  of  the 
party  ?  Is  it  not  possible  she  may  have  been  misrepre- 
sented? Have  not  men  of  genius  in  former  ages  often 
made  their  own  dreams  to  pass  for  her  oracles?  Ought 
she  then  to  be  condemned  without  any  further  hearing  ? 
This  would  be  unreasonable.  I  have  found  her  in  all 
other  matters  an  agreeable  companion,  a  faithful  coun- 
sellor, a  friend  to  common  sense,  and  to  the  happiness 
of  mankind.  This  justly  entitles  her  to  my  correspond- 
ence and  confidence,  till  I  find  infallible  proofs  of  her 
infidelity. 


CH.  II.,  SEC.  I.  THE  PHILOSOPHY  OF  REID.  89 

CHAPTER    II. 

OF  SMELLING. 

Section  I. 

THE  ORDER  OF  PROCEEDING OF  THE  MEDIUM  AND  ORGAN 

OF  SMELL. 

IT  is  so  difficult  to  unravel  the  operations  of  the  hu- 
man understanding,  and  to  reduce  them  to  their  first 
principles,  that  we  cannot  expect  to  succeed  in  the  at- 
tempt, but  by  beginning  with  the  simplest,  and  proceed- 
ing by  very  cautious  steps  to  the  more  complex.  The 
five  external  senses  may,  for  this  reason,  claim  to  be  first 
considered  in  an  analysis  of  the  human  faculties.  And 
the  same  reason  ought  to  determine  us  to  make  a  choice 
even  among  the  senses,  and  to  give  the  precedence, 
not  to  the  noblest  or  most  useful,  but  to  the  simplest, 
and  that  whose  objects  are  least  in  danger  of  being  mis- 
taken for  other  things. 

In  this  view,  an  analysis  of  our  sensations  may  be 
carried  on,  perhaps  with  most  ease  and  distinctness,  by 
taking  them  in  this  order:  Smelling,  Tasting,  Hearing, 
Touch,  and,  last  of  all,  Seeing. 

Natural  philosophy  informs  us,  that  all  animal  and 
vegetable  bodies,  and  probably  all  or  most  other  bodies, 
while  exposed  to  the  air,  are  continually  sending  forth 
effluvia  of  vast  subtilty,  not  only  in  their  state  of  life 
and  growth,  but  in  the  states  of  fermentation  and  putre- 
faction. These  volatile  particles  do  probably  repel  each 
other,  and  so  scatter  themselves  in  the  air,  until  they 
meet  with  other  bodies  to  which  they  have  some  chemi- 
cal affinity,  and  with  which  they  unite,  and  form  new 
concretes.  All  the  smell  of  plants,  and  of  other  bodies, 


90  THE  PHILOSOPHY  OF  REID.  LCH.  II. 

is  caused  by  these  volatile  parts,  and  is  smelled  wherever 
they  are  scattered  in  the  air :  and  the  acuteness  of  smell 
in  some  animals,  shews  us,  that  these  effluvia  spread  far, 
and  must  be  inconceivably  subtile. 

Whether,  as  some  chemists  conceive,  every  species  of 
bodies  hath  a  spiritus  rector,  a  kind  of  soul,  which  causes 
the  smell  and  all  the  specific  virtues  of  that  body,  and 
which,  being  extremely  volatile,  flies  about  in  the  air 
in  quest  of  a  proper  receptacle,  I  do  not  inquire.  This, 
like  most  other  theories,  is  perhaps  rather  the  product 
of  imagination  than  of  just  induction.  But  that  all 
bodies  are  smelled  by  means  of  effluvia  which  they  emit, 
and  which  are  drawn  into  the  nostrils  along  with  the 
air,  there  is  no  reason  to  doubt.  So  that  there  is  mani- 
fest appearance  of  design  in  placing  the  organ  of  smell 
in  the  inside  of  that  canal,  through  which  the  air  is  con- 
tinually passing  in  inspiration  and  expiration. 

Anatomy  informs  us,  that  the  membrana  pituitaria,  and 
the  olfactory  nerves,  which  are  distributed  to  the  villous 
parts  of  this  membrane,  are  the  organs  destined  by  the 
wisdom  of  nature  to  this  sense;  so  that  when  a  body  emits 
no  effluvia,  or  when  they  do  not  enter  into  the  nose,  or 
when  the  pituitary  membrane  or  olfactory  nerves  are 
rendered  unfit  to  p'erform  their  office,  it  cannot  be  smelled. 

Yet,  notwithstanding  this,  it  is  evident  that  neither  the 
organ  of  smell,  nor  the  medium,  nor  any  motions  we 
can  conceive  excited  in  the  membrane^  above  mentioned, 
or  in  the  nerve  or  animal  spirits,  do  in  the  least  resem- 
ble the  sensation  of  smelling;  nor  could  that  sensation  of 
itself  ever  have  led  us  to  think  of  nerves,  animal  spirits, 
or  effluvia. 

Section  II. 

THE  SENSATION  CONSIDERED  ABSTRACTLY. 

Having  premised  these  things  with  regard  to  the  me- 
dium and  organ  of  this  sense,  let  us  now  attend  careful- 


SEC.  II.]  THE  PHILOSOPHY  OF  REID.  91 

ly  to  what  the  mind  is  conscious  of  when  we  smell  a  rose 
or  a  lily;  and,  since  our  language  affords  no  other  name 
for  this  sensation,  we  shall  call  it  a  smell  or  odour,  care- 
fully excluding  from  the  meaning  of  those  names  every- 
thing but  the  sensation  itself,  at  least  till  we  have  ex- 
amined it. 

^  Suppose  a  person  who  never  had  this  sense  before,  to 
receive  it  all  at  once,  and  to  smell  a  rose — can  he  per- 
ceive any  similitude  or  agreement  between  the  smell  and 

\  the  rose?  or  indeed  between  it  and  any  other  object  what- 
soever? Certainly  he  cannot.  He  finds  himself  affected 
in  a  new  way,  he  knows  not  why  or  from  what  cause. 
Like  a  man  that  feels  some  pain  or  pleasure,  formerly  un- 
known to  him,  he  is  conscious  that  he  is  not  the  cause 
of  it  himself;  but  cannot,  from  the  nature  of  the  thing, 
determine  whether  it  is  caused  by  body  or  spirit,  by 
something  near,  or  by  something  at  a  distance.  It  has 
no  similitude  to  anything  else,  so  as  to  admit  of  a  com- 
parison; and,  therefore,  he  can  conclude  nothing  from  it, 
unless,  perhaps,  that  there  must  be  some  unknown 
cause  of  it. 

It  is  evidently  ridiculous  to  ascribe  to  it  figure,  colour, 
extension,  or  any  other  quality  of  bodies.  He  cannot 
give  it  a  place,  any  more  than  he  cain  give  a  place  to 
melancholy  or  joy;  nor  can  he  conceive  it  to  have  any 
existence, '  but  when  it  is  smelled.  So  that  it  appears  to 
be  a  simple  and  original  affection  or  feeling  of  the  mind, 
altogether  inexplicable  and  unaccountable.  It  is,  in- 
deed, impossible  that  it  can  be  in  any  body:  it  is  a  sen- 
sation, and  a  sensation  can  only  be  in  a  sentient  thing. 
The  various  odours  have  each  their  different  degrees  of 
strength  or  weakness.  Most  of  them  are  agreeable  or 
disagreeable;  and  frequently  those  that  are  agreeable 
when  weak,  are  disagreeable  when  stronger.  When  we 
compare  different  smells  together,  we  can  perceive  very 
few  resemblances  or  contrarieties,  or,  indeed,  relations 
of  any  kind  between  them.  They  are  all  so  simple  in 


92  THE  PHILOSOPHY  OF  REID.  |Cn.  II. 

themselves,  and  so  different  from  each  other,  that  it  is 
hardly  possible  to  divide  them  into  genera  and  species. 
Most  of  the  names  we  give  them  are  particular;  as  the 
smell  of  a  rose,  of  a  jessamine,  and  the  like.  Yet  there 
are  some  general  names — as  sweet,  stinking,  musty,  putrid, 
cadaverous,  aromatic.  Some  of  them  seem  to  refresh  and 
animate  the  mind,  others  to  deaden  and  depress  it. 


Section  III. 

SENSATION    AND     REMEMBRANCE,     NATURAL     PRINCIPLES    OF 
BELIEF. 

So  far  we  have  considered  this  sensation  abstractly. 
Let  us  next  compare  it  with  other  things  to  which  it 
bears  some  relation.  And  first  I  shall  compare  this  sen- 
sation with  the  remembrance,  and  the  imagination  of  it. 

I  can  think  of  the  smell  of  a  rose  when  I  do  not  smell  it; 
and  it  is  possible  that  when  I  think  of  it,  there  is  neither 
rose  nor  smell  anywhere  existing.  But  when  I  smell 
it,  I  am  necessarily  determined  to  believe  that  the  sen- 
sation really  exists.  This  is  common  to  all  sensations, 
that,  as  they  cannot  exist  but  in  being  perceived,  so  they 
cannot  be  perceived  but  they  must  exist.  I  could  as 
easily  doubt  of  my  own  existence,  as  of  the  existence  of 
my  sensations.  Even  those  profound  philosophers  who 
have  endeavoured  to  disprove  their  own  existence,  have 
yet  left  their  sensations  to  stand  upon  their  own  bottom, 
stript  of  a  subject,  rather  than  call  in  question  the  reali- 
ty of  their  existence. 

Here,  then,  a  sensation,  a  smell,  for  instance,  may  be 
presented  to  the  mind  three  different  ways:  it  may  be 
smelled,  it  may  be  remembered,  it  may  be  imagined  or 
thought  of.  In  the  first  case,  it  is  necessarily  accom- 
panied with  a  belief  of  its  present  existence;  in  the  sec- 
ond, it  is  necessarily  accompanied  with  a  belief  of  its  past 
existence;  and  in  the  last,  it  is  not  accompanied  with  be- 


SEC.  HI.]  THE  PHILOSOPHY   OF   REID.  93 

lief  at  all,*  but  is  what  the  logicians  call  a  simple  appre- 
hension. 

Why  sensation  should  compel  our  belief  of  the  pres- 
ent existence  of  the  thing,  memory  a  belief  of  its  past  ex- 
istence, and  imagination  no  belief  at  all,  I  believe  no 
philosopher  can  give  a  shadow  of  reason,  but  that  such 
is  the  nature  of  these  operations:  they  are  all  simple  and 
original,  and  therefore  inexplicable  acts  of  the  mind. 

Suppose  that  once,  and  only  once,  I  smelled  a  tube- 
rose in  a  certain  room,  where  it  grew  in  a  pot,  and  gave 
a  very  grateful  perfume.  Next  day  I  relate  what  I  saw 
and  smelled.  When  I  attend  as  carefully  as  I  can  to 
what  passes  in  my  mind  in  this  case,  it  appears  evident 
that  the  very  thing  I  saw  yesterday,  and  the  fragrance  I 
smelled,  are  now  the  immediate  objects  of  my  mind, 
when  I  remember  it.  Further,  I  can  imagine  this  pot 
and  flower  transported  to  the  room  where  I  now  sit,  and 
yielding  the  same  perfume.  Here  likewise  it  appears, 
that  the  individual  thing  which  I  saw  and  smelled,  is 
the  object  of  my  imagination. 

Philosophers  indeed  tell  me,  that  the  immediate  ob- 
ject of  my  memory  and  imagination-  in  this  case,  is  not 
the  past  sensation,  but  an  idea  of  it,  an  image,  phan- 
tasm, or  species,  f  of  the  odour  I  smelled:  that  this  idea 
now  exists  in  my  mind,  or  in  my  sensorium;  and  the 
mind,  contemplating  this  present  idea,  finds  it  a  repre- 
sentation of  what  is  past,  or  of  what  may  exist;  and  ac- 
cordingly calls  it  memory,  or  imagination.  This  is  the 
doctrine  of  the  ideal  philosophy;  which  we  shall  not 

*  This  is  not  strictly  correct.  The  imagination  of  an  object  is 
necessarily  accompanied  with  a  belief  of  the  existence  of  the  mental 
representation.  Reid  uses  the  term  existence  for  objective  existence 
only,  and  takes  no  account  of  the  possibility  of  a  subjective  exist- 
ence.—H. 

f  It  will  be  observed,  that  Reid  understands  by  Idea,  Image, 
Phantasm,  Species,  &•¥.,  always  a  tertiumquid numerically  different 
both  from  the  Object  existing  and  from  the  Subject  knowing.  He 
had  formed  no  conception  of  a  doctrine  in  which  a  representative  ob- 


94  THE  PHILOSOPHY  OF  REID.  [CH.  il. 

now  examine,  that  we  may  not  interrupt  the  thread  of 
the  present  investigation.  Upon  the  strictest  attention, 
memory  appears  to  me  to  have  things  that  are  past,  and 
not  present  ideas,  for  its  object.  We  shall  afterwards 
examine  this  system  of  ideas,  and  endeavour  to  make  it 
appear,  that  no  solid  proof  has  ever  been  advanced  of 
.  the  existence  of  ideas;  that  they  are  a  mere  fiction  and 
hypothesis,  contrived  to  solve  the  phenomena  of  the 
human  understanding;  that  they  do  not  at  all  answer 
this  end;  and  that  this  hypothesis  of  ideas  or  images  of 
things  in  the  mind,  or  in  the  sensorium,  is  the  parent  of 
those  many  paradoxes  so  shocking  to  common  sense, 
and  of  that  scepticism  which  disgrace  our  philosophy  of 
the  mind,  and  have  brought  upon  it  the  ridicule  and 
contempt  of  sensible  men. 

In  the  meantime,  I  beg  leave  to  think,  with  the  vul- 
gar, that,  when  I  remember  the  smell  of  the  tuberose, 
that  very  sensation  which  I  had  yesterday,  and  which 
has  now  no  more  any  existence,  is  the  immediate  object 
of  my  memory;  and  when  I  imagine  it  present,  the  sen- 
sation itself,  and  not  any  idea  of  it,  is  the  object  of  my 
imagination.  But,  though  the  object  of  my  sensation, 
memory,  and  imagination,  be  in  this  case  the  same,  yet 
these  acts  or  operations  of  the  mind  are  as  different,  and 
as  easily  distinguishable,  as  smell,  taste,  and  sound.  I 
am  conscious  of  a  difference  in  kind  between  sensation 
and  memory,  and  between  both  and  imagination.  I 
find  this  also,  that  the  sensation  compels  my  belief  of  the 
present  existence  of  the  smell,  and  memory  my  belief  of 
its  past  existence.  There  is  a  smell,  is  the  immediate 
testimony  of  sense;  there  was  a  smell,  is  the  immediate 
testimony  of  memory.  If  you  ask  me,  why  I  believe 
that  the  smell  exists,  I  can  give  no  other  reason,  nor 

ject  is  allowed,  but  only  as  a  modification  of  the  mind  itself.  On 
the  evil  consequences  of  this  error,  both  on  his  own  philosophy  and 
on  his  criticism  of  other  opinions, — H. 


SEC.  IV.]  THE  PHILOSOPHY  OF  RElD.  95 

shall  ever  be  able  to  give  any  other,  than  that  I  smell  it. 
If  you  ask,  why  I  believe  that  it  existed  yesterday,  I  can 
give  no  other  reason  but  that  I  remember  it. 

Sensation  and  memory,  therefore,  are  simple,  original,  , 
and  perfectly  distinct  operations  of  the  mind,  and  both 
of  them  are  original  principles  of  belief.  Imagination  is 
distinct  from  both,  but  is  no  principle  of  belief.  Sen- 
sation implies  the  present  existence  of  its  object,  mem- 
ory its  past  existence,  but  imagination  views  its  object 
naked,  and  without  any  belief  of  its  existence  or  non- 
existence,  and  is  therefore  what  the  schools  call  Simple 
Apprehension.  * 

Section  IV. 

JUDGMENT  AND  BELIEF  IN  SOME    CASES    PRE-CEDE    SIMPLE    AP- 
PREHENSION. ^ 

But  here,  again,  the  ideal  system  comes  in/ourjwayj_Jt 
teaches  us  that  the  first  operation  of  the  mincTabout  its 
ideas,  is  simple  apprehension — that  is,  the  bare  concep- 
tion of  a  thing  without  any  belief  about  it:   and  that, 
after  we  have  got  simple   apprehensions,  by  comparing 
them  together,  we  perceive  agreements  or  disagreements  / 
between  them;  and  that  this  perception  of  the  agreement/ 
or  disagreement  of  ideas,  is  all  that  we  call  belief,  judg/ 
ment,  or  knowledge.     Now,  this  appears  to  me   to  be 
all  fiction,  without  any  foundation  in   nature;  for   it  is 
acknowledged   by   all,   that   sensation   must  go  before 
memory  and  imagination;  and   hence  it  necessarily  fol-      x\     \r 
lows,  that  apprehension,  accompanied  with  belief  and  J  J^T 
knowledge,  must  go  before  simple  apprehension,  at  least 
in  the  matters  we  are  now  speaking  of.     So  that  here,  in- 


*  Simple  Apprehension,  in  the  language  of  the  Schools,  has  no 
reference  to  any  exclusion  of  belief.  It  was  merely  given  to  the  con- 
ception of  simple,  in  contrast  to  the  cognition  of  complex,  terms. 


96  THE  PHILOSOPHY  OF  REID.  [Cn.  II. 

stead  of  saying  that  the  belief  or  knowledge  is  got  by  put- 
ting together  and  comparing  the  simple  apprehensions, 
we  ought  rather  to  say  that  the  simple  apprehension  is  per- 
formed by  resolving  and  analysing  a  natural  and  origi- 
nal judgment.  And  it  is  with  the  operations  of  the 
mind,  in  this  case,  as  with  natural  bodies,  which  are, 
indeed,  compounded  of  simple  principles  or  elements. 
Nature  does  not  exhibit  these  elements  separate,  to 
be  compounded  by  us;  she  exhibits  them  mixed  and 
compounded  in  concrete  bodies,  and  it  is  only  by  art 
and  chemical  analysis  that  they  can  be  separated. 

Section  V. 

TWO  THEORIES  OF  THE    NATURE    OF    BELIEF   REFUTED — CON- 
CLUSIONS FROM  WHAT  HATH    BEEN  SAID. 

But  what  is  this  belief  or  knowledge  which  accompa- 
nies sensation  and  memory  ?  Every  man  knows  what  it 
is,  but  no  man  can  define  it.  Does  any  man  pretend  to 
define  sensation,  or  to  define  consciousness  ?  It  is  hap- 
py, indeed,  that  no  man  does.  And  if  no  philosopher 
had  endeavoured  to  define  and  explain  belief,  some  par- 
adoxes in  philosophy,  more  incredible  than  ever  were 
brought  forth  by  the  most  abject  superstition  or  the  most 
frantic  enthusiasm,  had  never  seen  the  light.  Of  this 
kind  surely  is  that  modern  discovery  of  the  ideal  philos- 
ophy, that  sensation,  memory,  belief,  and  imagination, 
when  they  have  the  same  object,  are  only  different  de- 
grees of  strength  and  vivacity  in  the  idea.  *  Suppose  the 
idea  to  be  that  of  a  future  state  after  death:  one  man  be- 
lieves it  firmly — this  means  no  more  than  that  he  hath  a 
strong  and  lively  idea  of  it;  another  neither  believes  nor 
disbelieves — that  is,  he  has  a  weak  and  faint  idea.  Sup- 
pose, now,  a  third  person  believes  firmly  that  there  is  no 

*  He  refers  to  Hume.— H. 


SBC.  V.]  THE  PHILOSOPHY   OF   REID.  97 

such  thing,  I  am  at  a  loss  to  know  whether  his  idea  be 
faint  or  lively:  if  it  is  faint,  then  there  may  be  a  firm  belief 
where  the  idea  is  faint;  if  the  idea  is  lively,  then  the  be- 
lief of  a  future  state  and  the  belief  of  no  future  state 
must  be  one  and  the  same.  The  same  arguments  that 
are  used  to  prove  that  belief  implies  only  a  stronger 
idea  of  the  object  than  simple  apprehension,  might  as 
well  be  used  to  prove  that  love  implies  only  a  stronger 
idea  of  the  object  than  indifference.  And  then  what 
shall  we  say  of  hatred,  which  must  upon  this  hypothe- 
sis be  a  degree  of  love,  or  a  degree  of  indifference  ?  If 
it  should  be  said,  that  in  love  there  is  something  more 
than  an  idea — to  wit,  an  affection  of  the  mind — may  it 
not  be  said  with  equal  reason,  that  in  belief  there  is  AJ 
something  more  than  an  idea — to  wit,  an  assent  or  per- 
suasion of  the  mind  ? 

But  perhaps  it  may  be  thought  as  ridiculous  to  argue 
against  this  strange  opinion,  as  to  maintain  it.  Indeed, 
if  a  man  should  maintain  that  a  circle,  a  square,  and  a 
triangle  differ  only  in  magnitude,  and  not  in  figure,  I 
believe  he  would  find  nobody  disposed  either  to  believe 
him  or  to  argue  against  him;  and  yet  I  do  not  think  it 
less  shocking  to  common  sense,  to  maintain  that  sensa- 
tion,  memory,  and  imagination  differ  only  in  degree, 
and  not  in  kind.  I  know  it  is  said,  that,  in  a  delirium, 
or  in  dreaming,  men  are  apt  to  mistake  one  for  the 
other.  But  does  it  follow  from  this,  that  men  who  are 
neither  dreaming  nor  in  a  delirium  cannot  distinguish 
them  ?  But  how  does  a  man  know  that  he  is  not  in  a 
delirium  ?  I  cannot  tell:  neither  can  I  tell  how  a  man 
knows  that  he  exists.  But,  if  any  man  seriously  doubts 
whether  he  is  in  a  delirium,  I  think  it  highly  probable 
that  he  is,  and  that  it  is  time  to  seek  for  a  cure,  which  I 
am  persuaded  he  will  not  find  in  the  whole  system  of 
logic. 

I  mentioned  before  Locke's  notion  of  belief  or  know- 
ledge ;  he  holds  that  it  consists  in  a  perception  of  the 


98  THE  PHILOSOPHY  OF  REID.  [Cn.  II. 

agreement  or  disagreement  of  ideas  ;  and  this  he  values 
himself  upon  as  a  very  important  discovery. 

We  shall  have  occasion  afterwards  to  examine  more 
particularly  this  grand  principle  of  Locke's  philosophy, 
and  to  shew  that  it  is  one  of  the  main  pillars  of  modern 
scepticism,  although  he  had  no  intention  to  make  that 
use  of  it.  At  present  let  us  only  consider  how  it  agrees 
with  the  instances  of  belief  now  under  consideration  ; 
and  whether  it  gives  any  light  to  them.  I  believe  that 
the  sensation  I  have  exists  ;  and  that  the  sensation  I 
remember  does  not  now  exist,  but  did  exist  yesterday. 
Here,  according  to  Locke's  system,  I  compare  the  idea 
of  a  sensation  with  the  ideas  of  past  and  present  exist- 
ence :  at  one  time  I  perceive  that  this  idea  agrees  with 
that  of  present  existence,  but  disagrees  with  that  of  past 
existence  ;  but,  at  another  time,  it  agrees  with  the  idea 
of  past  existence,  and  disagrees  with  that  of  present  ex- 
istence. Truly  these  ideas  seem  to  be  very  capricious 
in  their  agreements  and  disagreements.  Besides,  I  can- 
not, for  my  heart,  conceive  what  is  meant  by  either.  I 
say  a  sensation  exists,  and  I  think  I  understand  clearly 
what  I  mean.  But  you  want  to  make  the  thing  clearer, 
and  for  that  end  tell  me,  that  there  is  an  agreement  be- 
tween the  idea  of  that  sensation  and  the  idea  of  existence. 
To  speak  freely,  this  conveys  to  me  no  light,  but 
darkness ;  I  can  conceive  no  otherwise  of  it,  than  as  an 
odd  and  obscure  circumlocution.  I  conclude,  then,  ' 
that  the  belief  which  accompanies  sensation  and  mem- 
ory, is  a  simple  act  of  the  mind,  which  cannot  be  de- 
fined. It  is,  in  this  respect,  like  seeing  and  hearing, 
which  can  never  be  so  defined  as  to  be  understood  by 
those  who  have  not  these  faculties ;  and  to  such  as 
have  them,  no  definition  can  make  these  operations 
more  clear  than  they  are  already.  In  like  manner, 
every  man  that  has  any  belief — and  he  must  be  a  curi- 
osity that  has  none — knows  perfectly  what  belief  is,  but 
can  never  define  or  explain  it.  I  conclude,  also,  that 


SKC.VI.]  THE  PHILOSOPHY  OF  REID.  99 

sensation,  memory,  and  imagination,  even  where  they 
have  the  same  object,  are  operations  of  a  quite  differ- 
ent nature,  and  perfectly  distinguishable  by  those  who 
are  sound  and  sober.  A  man  that  is  in  danger  of  con- 
founding them,  is  indeed  to  be  pitied ;  but  whatever 
relief  he  may  find  from  another  art,  he  can  find  none 
from  logic  or  metaphysic.  I  conclude  further,  that  it  is 
no  less  a  part  of  the  human  constitution,  to  believe  the 
present  existence  of  our  sensations,  and  to  believe  the 
past  existence  of  what  we  remember,  than  it  is  to  believe 
that  twice  two  make  four.  The  evidence  of  sense,  the 
evidence  of  memory,  and  the  evidence  of  the  necessary 
relations  of  things,  are  all  distinct  and  original  kinds  of 
evidence,  equally  grounded  on  our  constitution  :  none 
of  them  depends  upon,  or  can  be  resolved  into  another. 
To  reason  against  any  of  these  kinds  of  evidence,  is 
absurd;  nay,  to  reason  for  them  is  absurd.  They  are 
first  principles ;  and  such  fall  not  within  the  province 
of  reason,  *  but  of  common  sense. 


Section    VI. 

APOLOGY  FOR  METAPHYSICAL  ABSURDITIES — SENSATION  WITH- 
OUT A  SENTIENT,  A  CONSEQUENCE  OF  THE  THEORY  OF 
IDEAS CONSEQUENCES  OF  THIS  STRANGE  OPINION. 

Having  considered  the  relation  which  the  sensation  of 
smelling  bears  to  the  remembrance  and  imagination  of 
it,  I  proceed  to  consider  what  relation  it  bears  to  a 
mind  or  sentient  principle.  It  is  certain,  no  man  can 
conceive  or  believe  smelling  to  exist  of  itself,  without  a 
mind,  or  something  that  has  the  power  of  smelling,  of 
which  it  is  called  a  sensation,  an  operation,  or  feeling. 
Yet,  if  any  man  should  demand  a  proof,  that  sensation 
cannot  be  without  a  mind  or  sentient  being,  I  confess 

*  See  note,  p.  79.— H. 


100  .       THE  PHILOSOPHY   OF  REID.  [Cn.  II. 

that  I  can  give  none ;  and  that  to  pretend  to  prove  it, 
seems  to  me  almost  as  absurd  as  to  deny  it. 

This  might  have  been  said  without  any  apology  before 
the  "Treatise  of  Human  Nature"  appeared  in  the 
world.  For  till  that  time,  no  man,  as  far  as  I  know, 
ever  thought  either  of  calling  in  question  that  principle, 
or  of  giving  a  reason  for  his  belief  of  it.  Whether 
thinking  beings  were  of  an  ethereal  or  igneous  nature, 
whether  material  or  immaterial,  was  variously  disputed; 
but  that  thinking  is  an  operation  of  some  kind  of  being 
or  other,  was  always  taken  for  granted,  as  a  principle 
that  could  not  possibly  admit  of  doubt. 

However,  since  the  author  above  mentioned,  who  is 
undoubtedly  one  of  the  most  acute  metaphysicians  that 
this  or  any  age  hath  produced,  hath  treated  it  as  a  vulgar 
prejudice,  and  maintained  that  the  mind  is  only  a  suc- 
cession of  ideas  and  impressions  without  any  subject; 
his  opinion,  however  contrary  to  the  common  appre- 
hensions of  mankind,  deserves  respect.  I  beg  there- 
fore, once  for  all,  that  no  offence  may  be  taken  at  charg- 
ing this  or  other  metaphysical  notions  with  absurdity, 
or  with  being  contrary  to  the  common  sense  of  mankind. 
No  disparagement  is  meant  to  the  understandings  of  the 
authors  or  maintainers  of  such  opinions.  Indeed,  they 
commonly  proceed,  not  from  defect  of  understanding, 
but  from  an  excess  of  refinement  the  reasoning  that 
leads  to  them  often  gives  new  light  to  the  subject,  and 
shews  real  genius  and  deep  penetration  in  the  author  ; 
and  the  premises  do  more  than  atone  for  the  conclu- 
sion. 

If  there  are  certain  principles,  as  I  think  there  are, 
which  the  constitution  of  our  nature  leads  us  to  believe, 
and  which  we  are  under  a  necessity  to  take  for  granted 
in  the  common  concerns  of  life,  without  being  able  to 
give  a  reason  for  them — these  are  what  we  call  the  prin- 
ciples of  common  sense  ;  and  what  is  manifestly  con- 
trary to  them,  is  what  we  call  absurd. 


SEC.  VI.]  THE  PHILOSOPHY  OF  REID.  IOI 

Indeed,  if  it  is  true,  and  to  be  received  as  a  principle 
of  philosophy,  that  sensation  and  thought  may  be  with- 
out a  thinking  being,  it  must  be  acknowledged  to  be  the 
most  wonderful  discovery  that  this  or  any  other  age  hath 
produced.  The  received  doctrine  of  ideas  is  the  princi- 
ple from  which  it  is  deduced,  and  of  which  indeed  it 
seems  to  be  a  just  and  natural  consequence.  And  it  is 
probable,  that  it  would  not  have  been  so  late  a  discov- 
ery, but  that  it  is  so  shocking  and  repugnant  to  the  com- 
mon apprehensions  of  mankind,  that  it  required  an  un- 
common degree  of  philosophical  intrepidity  to  usher  it 
into  the  world.  It  is  a  fundamental  principle  of  the  ideal 
system,  that  every  object  of  thought  must  be  an  impres- 
sion or  an  idea — that  is,  a  faint  copy  of  some  preceding 
impression.  This  is  a  principle  so  commonly  received, 
that  the  author  above  mentioned,  although  his  whole  sys- 
tem is  built  upon  it,  never  offers  the  least  proof  of  it.  It 
is  upon  this  principle,  as  a  fixed  point,  that  he  erects  his 
metaphysical  engines,  to  overturn  heaven  and  earth,  body 
and  spirit.  And,  indeed,  in  my  apprehension,  it  is  alto- 
gether sufficient  for  the  purpose.  For,  if  impressions 
and  ideas  are  the  only  objects  of  thought,  then  heaven 
and  earth,  and  body  and  spirit,  and  everything  you 
please,  must  signify  only  impressions  and  ideas,  or  they 
must  be  words  without  any  meaning.  It  seems,  there- 
fore, that  this  notion,  however  strange,  is  closely  con- 
nected with  the  received  doctrine  of  ideas,  and  we  must 
either  admit  the  conclusion,  or  call  in  question  the 
premises. 

Ideas  seem  to  have  something  in  their  nature  un- 
friendly to  other  existences.  They  were  first  introduced 
into  philosophy,  in  the  humble  character  of  images  or 
representatives  of  things  :  and  in  this  character  they 
seemed  not  only  to  be  inoffensive,  but  to  serve  admir- 
ably well  for  explaining  the  operations  of  the  human  un- 
derstanding. But,  since  men  began  to  reason  clearly 
and  distinctly  about  them,  they  h rjJoJ  lirgrrr"  sup- 

^5^ 
OP 


102  THE  PHILOSOPHY   OF  REID.  [CH.II. 

planted  their  constituents,  and  undermined  the  existence  of 
everything  but  themselves.  First,  they  discarded  all  sec- 
ondary qualities  of  bodies ;  and  it  was  found  out  by 
their  means,  that  fire  is  not  hot,  nor  snow  cold,  nor 
honey  sweet ;  and,  in  a  word,  that  heat  and  cold,  sound, 
colour,  taste,  and  smell,  are  nothing  but  ideas  or  impres- 
sions. Bishop  Berkeley  advanced  them  a  step  higher, 
and  found  out,  by  just  reasoning  from  the  same  princi- 
ples, that  extension,  solidity,  space,  figure,  and  body, 
are  ideas,  and  that  there  is  nothing  in  nature  but  ideas 
and  spirits.  But  the  triumph  of  ideas  was  completed  by 
the  "Treatise  of  Human  Nature/'  which  discards  spirits 
also,  and  leaves  ideas  and  impressions  as  the  sole  exist- 
ences in  the  universe.  What  if,  at  last,  having  nothing 
else  to  contend  with,  they  should  fall  foul  of  one  another, 
and  leave  no  existence  in  nature  at  all  ?  This  would 
surely  bring  philosophy  into  danger  ;  for  what  should 
we  have  left  to  talk  or  to  dispute  about  ? 

However,  hitherto  these  philosophers  acknowledge 
the  existence  of  impressions  and  ideas  ;  they  acknow- 
ledge certain  laws  of  attraction,  or  rules  of  precedence, 
according  to  which,  ideas  and  impressions  range  them- 
selves in  various  forms,  and  succeed  one  another  :  but 
that  they  should  belong  to  a  mind,  as  its  proper  goods 
and  chattels,  this  they  have  found  to  be  a  vulgar  error. 
These  ideas  are  as  free  and  independent  as  the  birds  of 
the  air,  or  as  Epicurus's  atoms  when  they  pursued  their 
journey  in  the  vast  inane.  Shall  we  conceive  them  like 
the  films  of  things  in  the  Epicurean  system  ? 

Principio  hoc  dice,  rerum  simulacra  vagari, 
Multa  modis  multis,  in  cunctas  undique  parteis 
Tenuia,  quae  facile  inter  se  junguntur  in  auris, 
Obvia  cum  veniunt—  LUCR. 

Or  do  they  rather  resemble  Aristotle's  intelligible  species, 
after  they  are  shot  forth  from  the  object,  and  before  they 
have  yet  struck  upon  the  passive  intellect  ?  But  why 


SEC.  VI.]  THE  PHILOSOPHY   OF  REID.  103 

should  we  seek  to  compare  them  with  anything,  since 
there  is  nothing  in  nature  but  themselves  ?  They  make 
the  whole  furniture  of  the  universe  ;  starting  into  exist- 
ence, or  out  of  it,  without  any  cause  ;  combining  into 
parcels,  which  the  vulgar  call  minds ;  and  succeeding 
one  another  by  fixed  laws,  without  time,  place,  or  author 
of  those  laws. 

Yet,  after  all,  these  self-existent  and  independent  ideas 
look  pitifully  naked  and  destitute,  when  left  thus  alone 
in  the  universe,  and  seem,  upon  the  whole,  to  be  in  a 
worse  condition  than  they  were  before.  Des  Cartes, 
Malebranche,  and  Locke,  as  they  made  much  use  of 
ideas,  treated  them  handsomely,  and  provided  them  in 
decent  accommodation ;  lodging  them  either  in  the  pineal 
gland,  or  in  the  pure  intellect,  or  even  in  the  divine 
mind.  They  moreover  clothed  them  with  a  commission, 
and  made  them  representatives  of  things,  which  gave  them 
some  dignity  and  character.  But  the  "Treatise  of  Hu- 
man Nature,"  though  no  less  indebted  to  them,  seems 
to  have  made  but  a  bad  return,  by  bestowing  upon  them 
this  independent  existence :  since  thereby  they  are 
turned  out  of  house  and  home,  and  set  adrift  in  the 
world,  without  friend  or  connection,  without  a  rag  to 
cover  their  nakedness ;  and  who  knows  but  the  whole 
system  of  ideas  may  perish  by  the  indiscreet  zeal  of  their 
friends  to  exalt  them  ? 

However  this  may  be,  it  is  certainly  a  most  amazing 
discovery  that  thought  and  ideas  may  be  without  any 
thinking  being — a  discovery  big  with  consequences 
which  cannot  easily  be  traced  by  those  deluded  mortals 
who  think  and  reason  in  the  common  track.  We  were 
always  apt  to  imagine,  that  thought  supposed  a  thinker, 
and  love  a  lover,  and  treason  a  traitor  :  but  this,  it  seems, 
was  all  a  mistake  ;  and  it  is  found  out,  that  there  may 
be  treason  without  a  traitor,  and  love  without  a  lover, 
laws  without  a  legislator,  and  punishment  without  a  suf- 
ferer, succession  without  time,  and  motion  without  any- 


104  THE  PHILOSOPHY   OF  REID,  |CH.  II. 

thing  moved,  or  space  in  which  it  may  move  :  or  if,  in 
these  cases,  ideas  are  the  lover,  the  sufferer,  the  traitor, 
it  were  to  be  wished  that  the  author  of  this  discovery 
had  farther  condescended  to  acquaint  us  whether  ideas 
can  converse  together,  and  be  under  obligations  of  duty 
or  gratitude  to  each  other  ;  whether  they  can  make 
promises  and  enter  into  leagues  and  covenants,  and  ful- 
fil or  break  them,  and  be  punished  for  the  breach.  If 
one  set  of  ideas  makes  a  covenant,  another  breaks  it, 
and  a  third  is  punished  for  it,  there  is  reason  to  think 
that  justice  is  no  natural  virtue  in  this  system. 

It  seemed  very  natural  to  think,  that  the  ' '  Treatise  of 
Human  Nature"  required  an  author,  and  a  very 
ingenious  one  too;  but  now  we  learn  that  it  is  only  a 
set  of  ideas  which  came  together  and  arranged  them- 
selves by  certain  associations  and  attractions. 

After  all,  this  curious  system  appears  not  to  be  fitted 
to  the  present  state  of  human  nature.  How  far  it  may 
suit  some  choice  spirits,  who  are  refined  from  the  dregs 
of  common  sense,  I  cannot  say.  It  is  acknowledged,  I 
think,  that  even  these  can  enter  into  this  system  only  in 
their  most  speculative  hours,  when  they  soar  so  high  in 
pursuit  of  those  self-existent  ideas  as  to  lose  sight  of  all 
other  things.  But  when  they  condescend  to  mingle 
again  with  the  human  race,  and  to  converse  with  a 
friend,  a  companion,  or  a  fellow-citizen,  the  ideal  sys- 
tem vanishes;  common  sense,  like  an  irresistible  torrent, 
carries  them  along;  and,  in  spite  of  all  their  reasoning 
and  philosophy,  they  believe  their  own  existence,  and 
the  existence  of  other  things. 

Indeed,  it  is  happy  they  do  so;  for,  if  they  should 
carry  their  closet  belief  into  the  world,  the  rest  of  man- 
kind would  consider  them  as  diseased,  and  send  them  to 
an  infirmary.  Therefore,  as  Plato  required  certain  pre- 
vious qualifications  of  those  who  entered  his  school,  I 
think  it  would  be  prudent  for  the  doctors  of  this  ideal 
philosophy  to  do  the  same,  and  to  refuse  admittance  to 


SEC.  VII.]  THE  PHILOSOPHY  OF  REID.  105 

every  man  who  is  so  weak  as  to  imagine  that  he  ought 
to  have  the  same  belief  in  solitude  and  in  company, 
or  that  his  principles  ought  to  have  any  influence  upon 
his  practice  ;  for  this  philosophy  is  like  a  hobby-horse, 
which  a  man  in  bad  health  may  ride  in  his  closet,  with- 
out hurting  his  reputation;  but,  if  he  should  take  him 
abroad  with  him  to  church,  or  to  the  exchange,  or  to  the 
play-house,  his  heir  would  immediately  call  a  jury,  and 
seize  his  estate. 

Section   VIL 

THE  CONCEPTION  AND  BELIEF  OF  A  SENTIENT  BEING  OR  MIND 
IS  SUGGESTED  BY  OUR  CONSTITUTION THE  NOTION  OF  RE- 
LATIONS NOT  ALWAYS  GOT  BY  COMPARING  THE  RELATED 
IDEAS. 

Leaving  this  philosophy,  therefore,  to  those  who  have 
occasion  for  it,  and  can  use  it  discreetly  as  a  chamber 
exercise,  we  may  still  inquire  how  the  rest  of  mankind, 
and  even  the  adepts  themselves,  except  in  some  solitary 
moments,  have  got  so  strong  and  irresistible  a  belief, 
that  thought  must  have  a  subject,  and  be  the  act  of  some 
thinking  being;  how  every  man  believes  himself  to  be 
something  distinct  from  his  ideas  and  impressions — some- 
thing which  continues  the  same  identical  self  when  all. 
his  ideas  and  impressions  are  changed.  It  is  impossible 
to  trace  the  origin  of  this  opinion  in  history;  for  all  lan- 
guages have  it  interwoven  in  their  original  construction. 
All  nations  have  always  believed  it.  The  constitution 
of  all  laws  and  governments,  as  well  as  the  common 
transactions  of  life,  suppose  it. 

It  is  no  less  impossible  for  any  man  to  recollect  when 
he  himself  came  by  this  notion;  for,  as  far  back  as  we 
can  remember,  we  were  already  in  possession  of  it,  and 
as  fully  persuaded  of  our  own  existence,  and  the  exist- 
ence of  other  things,  as  that  one  and  one  make  two.  It 
seems,  therefore,  that  this  opinion  preceded  all  reasoning, 


106  THE  PHILOSOPHY  OF  REID.  [Cn.ll. 

and  experience,  and  instruction;  and  this  is  the  more 
probable,  because  we  could  not  get  it  by  any  of  these 
means.  It  appears,  then,  to  be  an  undeniable  fact,  that, 
from  thought  or  sensation,  all  mankind,  constantly  and 
invariably,  from  the  first  dawning  of  reflection,  do  infer 
a  power  or  faculty  of  thinking  and  a  permanent  being 
or  mind  to  which  that  faculty  belongs;  and  that  we  as 
invariably  ascribe  all  the  various  kinds  of  sensation  and 

•  thought  we  are  conscious  of,  to  one  individual  mind  or 
self. 

But  by  what  rules  of  logic  we  make  these  inferences, 
it  is  impossible  to  shew;  nay,  it  is  impossible  to  shew 
how  our  sensations  and  thoughts  can  give  us  the  very 
notion  and  conception  either  of  a  mind  or  of  a  faculty. 
The  faculty  of  smelling  is  something  very  different  from 
the  actual  sensation  of  smelling;  for  the  faculty  may  re- 
main when  we  have  no  sensation.  And  the  mind  is  no 

-,  less  different  from  the  faculty;  for  it  continues  the  same 
individual  being  when  that  faculty  is  lost.  Yet  this  sen- 
sation suggests  to  us  both  a  faculty  and  a  mind;  and  not 
only  suggests  the  notion  of  them,  but  creates  a  belief  of 
their  existence;  although  it  is  impossible  to  discover,  by 
reason,  any  tie  or  connection  between  one  and  the 
other. 

What  shall  we  say,  then  ?  Either  those  inferences 
which  we  draw  from  our  sensations — namely,  the  exist- 
ence of  a  mind,  and  of  powers  or  faculties  belonging  to 
it — are  prejudices  of  philosophy  or  education,  mere  fic- 
tions of  the  mind,  which  a  wise  man  should  throw  off 
as  he  does  the  belief  of  fairies;  or  they  are  judgments  of 
nature — judgments  not  got  by  comparing  ideas,  and  per- 
ceiving agreements  and  disagreements,  but  immediately 
inspired  by  our  constitution^ 

If  this  last  is  the  case,  as  I  apprehend  it  is,  it  will  be 
impossible  to  shake  off  those  opinions,  and  we  must 
yield  to  them  at  last,  though  we  struggle  hard  to  get  rid 
of  them.  And  if  we  could,  by  a  determined  obstinacy, 


SEC.  VII.]  THE  PHILOSOPHY  OF  REID.  IO7 

shake  off  the  principles  oF  our  nature,  this  is  not  to  act 
the  philosopher,  but  the  fool  or  the  madman.  It  is  in> 
cumbent  upon  those  who  think  that  these  are  not 
natural  principles,  to  shew,  in  the  first  place,  how  we 
can  otherwise  get  the  notion  of  a  mind  and  its  faculties; 
and  then  to  shew  how  we  come  to  deceive  ourselves  into 
the  opinion  that  sensation  cannot  be  without  a  sentient 
being. 

It  is  the  received  doctrine  of  philosophers,  that  our 
notions  of  relations  can  only  be  got  by  comparing  the 
related  ideas:  but,  in  the  present  case,  there  seems  to  be 
an  instance  to  the  contrary.  It  is  not  by  having  first 
the  notions  of  mind  and  sensation,  and  then  comparing 
them  together,  that  we  perceive  the  one  to  have  the  rela- 
tion of  a  subject  or  substratum,  and  the  other  that  of  an 
act  or  operation:  on  the  contrary,  one  of  the  related 
things — to  wit,  sensation — suggests  to  us  both  the  cor- 
relate and  the  relation. 

I  beg  leave  to  make  use  of  the  word  suggestion,  be- 
cause I  know  not  one  more  proper,  to  express  a  power 
of  the  mind,  which  seems  entirely  to  have  escaped  the 
notice  of  philosophers,  and  to  which  we  owe  many  of 
our  simple  notions  which  are  neither  impressions  nor 
ideas,  as  well  as  many  original  principles  of  belief. 
I  shall  endeavor  to  illustrate,  by  an  example,  what  I 
understand  by  this  word.  We  all  know,  that  a  certain 
kind  of  sound  suggests  immediately  to  the  mind,  a 
coach  passing  in  the  street;  and  not  only  produces  the 
imagination,  but  the  belief,  that  a  coach  is  passing.  Yet 
there  is  here  no  comparing  of  ideas,  no  perception  of 
agreements  or  disagreements,  to  produce  this  belief:  nor 
is  there  the  least  similitude  between  the  sound  we  hear 
and  the  coach  we  imagine  and  believe  to  be  passing.* 


*  "The  word  suggest  "  (says  Mr.  Stewart,  in  reference  to  the  pre- 
ceding passage)  "is  much  used  by  Berkeley,  in  this  appropriate  and 
technical  sense,  not  only  in  his  '  Theory  of  Vision, '  but  in  his  *  Prin- 


108  THE  PHILOSOPHY  OF  REID.  [Cn.  II. 

It  is  true  that  this  suggestion  is  not  natural  and  original; 
if  is  the  result  of  experience  and  habit.  But  I  think  it 
appears,  from  what  hath  been  said,  that  there  are  natural 
suggestions:  particularly,  that  sensation  suggests  the  no- 
tion of  present  existence,  and  the  belief  that  what  we 
perceive  or  feel  does  now  exist;  that  memory  suggests  the 
notion  of  past  existence,  and  the  belief  that  what  we 
remember  did  exist  in  time  past;  and  that  our  sensations 
and  thoughts  do  also  suggest  the  notion  of  a  mind,  and 
the  belief  of  its  existence,  and  of  its  relation  to  our 


ciples  of  Human  Knowledge,'  and  in  his  '  Minute  Philosopher.'  It 
expresses,  indeed,  the  cardinal  principle  on  which  his  '  Theory  of 
Vision '  hinges,  and  is  now  so  incorporated  with  some  of  our  best 
metaphysical  speculations,  that  one  cannot  easily  conceive  how 
the  use  of  it  was  so  long  dispensed  with.  Locke  uses  the  word  excite 
for  the  same  purpose;  but  it  seems  to  imply  an  hypothesis  concerning 
the  mechanism  of  the  mind,  and  by  no  means  expresses  the  fact  in 
question  with  the  same  force  and  precision. 

"It is  remarkable,  that  Dr.  Reid  should  have  thought  it  incum- 
bent on  him  to  apologise  for  introducing  into  philosophy  a  word  so 
familiar  to  every  person  conversant  with  Berkeley's  works.  « I  beg 
leave  to  make  use  of  the  word  suggestion,  because, '  &c 

"  So  far  Dr.  Reid's  use  of  the  word  coincides  exactly  with  that  of 
Berkeley ;  but  the  former  will  be  found  to  annex  to  it  a  meaning 
more  extensive  than  the  latter,  by  employing  it  to  comprehend,  not 
only  those  intimations  which  are  the  result  of  experience  and  habit; 
but  another  class  of  intimations,  (quite  overlooked  by  Berkeley,) 
those  which  result  from  the  original  frame  of  the  human  mind." — 
Dissertation  on  the  History  of  Metaphysical  and  Ethical  Science. 
P.  167.  Second  edition. 

Mr.  Stewart  might  have  adduced,  perhaps,  a  higher  and,  certainly, 
a  more  proximate  authority,  in  favour,  not  merely  of  the  term  in 
general,  but  of  Reid's  restricted  employment  of  it,  as  an  intimation 
of  what  he  and  others  have  designated  the  Common  Sense  of  man- 
kind. The  following  sentence  of  Tertullian  contains  a  singular  an- 
ticipation, both  of  the  philosophy  and  of  the  philosophical  phrase- 
ology of  our  author.  Speaking  of  the  universal  belief  of  the  soul's 
immortality: — "  Natura pleraque  suggeruntur,  quasi  de  flttblico sensu 
quo  animam  Deus  ditare  dignatus  est." — DE  ANIMA,  c.  2. 

Some  strictures  on  Reid's  employment  of  the  term  suggestion  may 
be  seen  in  the  "  Versuche"  of  Tetens,  I.,  p.  508,  sqq. — H. 


SEC.  VIII.]  THE  PHILOSOPHY  OF  REID.  109 

thoughts.  By  a  like  natural  principle  it  is,  that  a  be- 
ginning of  existence,  or  any  change  in  nature,  suggests 
to  us  the  notion  of  a  cause,  and  compels  our  belief  of  its 
existence.  And,  in  like  manner,  as  shall  be  shewn  when 
we  come  to  the  sense  of  touch,  certain  sensations  of 
touch,  by  the  constitution  of  our  nature,  suggest  to  us 
extension,  solidity,  and  motion,  which  are  nowise  like 
to  sensations,  although  they  have  been  hitherto  con- 
founded with  them. 

Section   VIII. 

THERE  IS  A  QUALITY  OR  VIRTUE  IN  BODIES,  WHICH  WE  CALL 
THEIR  SMELL HOW  THIS  IS  CONNECTED  IN  THE  IMAGINA- 
TION WITH  THE  SENSATION. 

We  have  considered  smell  as  signifying  a  sensation, 
feeling,  or  impression  upon  the  mind;  and  in  this  sense, 
it  can  only  be  in  a  mind,  or  sentient  being:  but  it  is  evi- 
dent that  mankind  gives  the  name  of  smell  much  more 
frequently  to  something  which  they  conceive  to  be  ex- 
ternal, and  to  be  a  quality  of  body:  they  understand 
something  by  it  which  does  not  at  all  infer  a  mind;  and 
have  not  the  least  difficulty  in  conceiving  the  air  per- 
fumed with  aromatic  odours  in  the  deserts  of  Arabia,  or 
in  some  uninhabited  island,  where  the  human  foot 
never  trod.  Every  sensible  day-labourer  hath  as  clear  a 
notion  of  this,  and  as  full  a  conviction  of  the  possibility 
of  it,  as  he  hath  of  his  own  existence;  and  can  no  more 
doubt  of  the  one  than  of  the  other. 

Suppose  that  such  a  man  meets  with  a  modern  phi- 
losopher, and  wants  to  be  informed  what  smell  in  plants 
is.  The  philosopher  tells  him,  that  there  is  no  smell 
in  plants,  nor  in  anything  but  in  the  mind;  that  it  is 
impossible  there  can  be  smell  but  in  a  mind;  and  that  all 
this  hath  been  demonstrated  by  modern  philosophy. 
The  plain  man  will,  no  doubt,  be  apt  to  think  him 
merry:  but,  if  he  finds  that  he  is  serious,  his  next  conclu- 


IIO  THE  PHILOSOPHY   OF  REID.  [CH.  ll. 

sion  will  be  that  he  is  mad;  or  that  philosophy,  like 
magic,  puts  men  into  a  new  world,  and  gives  them 
different  faculties  from  common  men.  And  thus  philoso- 
phy and  common  sense  are  set  at  variance.  But  who  is 
to  blame  for  it  ?  In  my  opinion  the  philosopher  is  to 
blame.  For  if  he  means  by  smell,  what  the  rest  of  man- 
kind most  commonly  mean,  he  is  certainly  mad.  But  if 
he  puts  a  different  meaning  upon  the  word,  without  ob- 
serving it  himself,  or  giving  warning  to  others,  he  abuses 
language  and  disgraces  philosophy,  without  doing  any 
service  to  truth:  as  if  a  man  should  exchange  the  mean- 
ing of  the  words  daughter  and  cow,  and  then  endeavour  to 
prove  to  his  plain  neighbour,  that  his  cow  is  his  daughter, 
and  his  daughter  his  cow. 

I  believe  there  is  not  much  more  wisdom  in  many  of 
those  paradoxes  of  the  ideal  philosophy,  which  to  plain 
sensible  men  appear  to  be  palpable  absurdities,  but  with 
the  adepts  pass  for  profound  discoveries.  I  resolve,  for 
my  own  part,  always  to  pay  a  great  regard  to  the  dictates 
of  common  sense,  and  not  to  depart  from  them  without 
absolute  necessity:  and,  therefore,  I  am  apt  to  think  that 
there  is  really  something  in  the  rose  or  lily,  which  is  by 
the  vulgar  called  smell,  and  which  continues  to  exist 
when  it  is  not  smelled:  and  shall  proceed  to  inquire  what 
this  is;  how  we  come  by  the  notion  of  it;  and  what  rela- 
tion this  quality  or  virtue  of  smdl  hath  to  the  sensation 
which  we  have  been  obliged  to  call  by  the  same  name, 
for  want  of  another. 

Let  us  therefore  suppose,  as  before,  a  person  begin- 
ning to  exercise  the  sense  of  smelling;  a  little  experience 
will  discover  to  him  that  the  nose  is  the  organ  of  this 
sense,  and  that  the  air,  or  something  in  the  air,  is  a 
medium  of  it.  And  finding,  by  farther  experience,  that, 
v  when  a  rose  is  near,  he  has  a  certain  sensation,  when  it 
is  removed,  the  sensation  is  gone,  he  finds  a  connection 
in  nature  betwixt  the  rose  and  this  sensation.  The  rose 
is  considered  as  a  cause,  occasion,  or  antecedent  of  the 


SEC.  IX.]  THE  PHILOSOPHY  OF  REID.  Ill 

sensation;  the  sensation  as  an  effect  or  consequence  of 
the  presence  of  the  rose;  they  are  associated  in  the  mind, 
and  constantly  found  conjoined  in  the  imagination. 

But  here  it  deserves  our  notice,  that,  although  the  sen- 
sation may  seem  more  closely  related  to  the  mind  its 
subject,  or  to  the  nose  its  organ,  yet  neither  of  these  con- 
nections operate  so  powerfully  upon  the  imagination  as 
its  connection  with  the  rose  its  concomitant.  The  reason 
of  this  seems  to  be,  that  its  connection  with  the  mind  is 
more  general,  and  noway  distinguisheth  it  from  other 
smells,  or  even  from  tastes,  sounds,  and  other  kinds  of 
sensations.  The  relation  it  hath  to  the  organ  is  likewise 
general,  and  doth  not  distinguish  it  from  other  smells; 
but  the  connection  it  hath  with  the  rose  is  special  and 
constant;  by  which  means  they  become  almost  insepa- 
rable in  the  imagination,  in  like  manner  as  thunder  and 
lightning,  freezing  and  cold. 


Section  IX. 

THAT  THERE  IS  A  PRINCIPLE  IN  HUMAN  NATURE,  FROM  WHICH 
THE  NOTION  OF  THIS,  AS  WELL  AS  ALL  OTHER  NATURAL 
VIRTUES  OR  CAUSES,  IS  DERIVED. 

In  order  to  illustrate  further  how  we  come  to  conceive 
a  quality  or  virtue  in  the  rose  which  we  call  smell,  and 
what  this  smell  is,  it  is  proper  to  observe,  that  the  mind 
begins  very  early  to  thirst  after  principles  which  may 
direct  it  in  the  exertion  of  its  powers.  The  smell  of  a 
rose  is  a  certain  affection  or  feeling  of  the  mind;  and,  as 
it  is  not  constant,  but  comes  and  goes,  we  want  to  know 
when  and  where  we  may  expect  it;  and  are  uneasy  till 
we  find  something  which,  being  present,  brings  this 
feeling  along  with  it,  and,  being  removed,  removes 
it.  This,  when  found,  we  call  the  cause  of  it;  not  in 
a  strict  and  philosophical  sense,  as  if  the  feeling  were 
really  effected  or  produced  by  that  cause,  but  in  a  popu- 


112  THE  PHILOSOPHY   OF  REID.  [Cn.  II. 

lar  sense;  for  the  mind  is  satisfied  if  there  is  a  constant 
conjunction  between  them;  and  such  causes  are  in  reality 
nothing  else  but  laws  of  nature.  Having  found  the  smell 
thus  constantly  conjoined  with  the  rose,  the  mind  is  at 
rest,  without  inquiring  whether  this  conjunction  is  owing 
to  a  real  efficiency  or  not;  that  being  a  philosophical 
inquiry,  which  does  not  concern  human  life.  But  every 
discovery  of  such  a  constant  conjunction  is  of  real  im- 
portance in  life,  and  makes  a  strong  impression  upon 
the  mind. 

So  ardently  do  we  desire  to  find  everything  that  hap- 
pens within  our  observation  thus  connected  with  some- 
thing else  as  its  cause  or  occasion,  that  we  are  apt  to 
fancy  connections  upon  the  slightest  grounds;  and  this 
weakness  is  most  remarkable  in  the  ignorant,  who  know 
least  of  the  real  connections  established  in  nature.  A 
man  meets  with  an  unlucky  accident  on  a  certain  day  of  the 
year,  and,  knowing  no  other  cause  of  his  misfortune,  he 
is  apt  to  conceive  something  unlucky  in  that  day  of  the 
calendar;  and,  if  he  finds  the  same  connection  hold  a 
second  time,  is  strongly  confirmed  in  his  superstition.  I 
remember,  many  years  ago,  a  white  ox  was  brought  into 
this  country,  of  so  enormous  a  size  that  people  came 
many  miles  to  see  him.  There  happened,  some  months 
after,  an  uncommon  fatality  among  women  in  child-bear- 
ing. Two  such  uncommon  events,  following  one  an- 
other, gave  a  suspicion  of  their  connection,  and  oc- 
casioned a  common  opinion  among  the  country-people 
that  the  white  ox  was  the  cause  of  this  fatality. 

However  silly  and  ridiculous  this  opinion  was,  it 
sprung  from  the  same  root  in  human  nature  on  which 
all  natural  philosophy  grows — namely,  an  eager  desire  to 
find  out  connections  in  things,  and  a  natural,  original, 
and  unaccountable  propensity  to  believe  that  the  con- 
nections which  we  have  observed  in  time  past  will 
continue  in  time  to  come.  Omens,  portents,  good  and 
bad  luck,  palmistry,  astrology,  all  the  numerous  arts  of 


SEC.  IX.]  THE   PHILOSOPHY   OF   REID.  113 

divination  and  of  interpreting  dreams,  false  hypotheses 
and  systems,  and  true  principles  in  the  philosophy  of 
nature,  are  all  built  upon  the  same  foundation  in  the 
human  constitution,  and  are  distinguished  only  accord- 
ing as  we  conclude  rashly  from  too  few  instances,  or 
cautiously  from  a  sufficient  induction. 

As  it  is  experience  only  that  discovers  these  connec- 
tions between  natural  causes  and  their  effects;  without 
inquiring  further,  we  attribute  to  the  cause  some  vague 
and  indistinct  notion  of  power  or  virtue  to  produce  the 
effect.  And,  in  many  cases,  the  purposes  of  life  do  not 
make  it  necessary  to  give  distinct  names  to  the  cause 
and  the  effect.  Whence  it  happens,  that,  being  closely 
connected  in  the  imagination,  although  very  unlike  to 
each  other,  one  name  serves  for  both;  and,  in  common 
discourse,  is  most  frequently  applied  to  that  which,  of 
the  two,  is  most  the  object  of  our  attention.  This  occa- 
sions an  ambiguity  in  many  words,  which,  having  the 
same  causes  in  all  languages,  is  common  to  all,  and  is 
apt  to  be  overlooked  even  by  philosophers.  Some 
instances  will  serve  both  to  illustrate  and  confirm  what 
we  have  said. 

Magnetism  signifies  both  the  tendency  of  the  iron  to- 
wards the  magnet,  and  the  power  of  the  magnet  to  pro- 
duce that  tendency;  and,  if  it  was  asked,  whether  it  is  a 
quality  of  the  iron  or  of  the  magnet,  one  would  perhaps 
be  puzzled  at  first;  but  a  little  attention  would  discover, 
that  we  conceive  a  power  or  virtue  in  the  magnet  as  the 
cause,  and  a  motion  in  the  iron  as  the  effect;  and, 
although  these  are  things  quite  unlike,  they  are  so  united 
in  the  imagination,  that  we  give  the  common  name  of 
magnetism  to  both.  The  same  thing  may  be  said  of 
gravitation,  which  sometimes  signifies  the  tendency  of 
bodies  towards  the  earth,  sometimes  the  attractive  power 
of  the  earth,  which  we  conceive  as  the  cause  of  that  ten- 
dency. We  may  observe  the  same  ambiguity  in  some 
of  Sir  Isaac  Newton's  definitions;  and  that  even  in  words 


114  THE  PHILOSOPHY   OF  REID.  [Cn.  II. 

of  his  own  making.  In  three  of  his  definitions,  he  ex- 
plains very  distinctly  what  he  understands  by  the  absolute 
quantity,  what  by  the  accelerative  quantity,  and  what  by 
the  motive  quantity,  of  a  centripetal  force.  In  the  first 
of  these  three  definitions,  centripetal  force  is  put  for  the 
cause,  which  we  conceive  to  be  some  power  or  virtue  in 
the  centre  or  central  body;  in  the  two  last,  the  same 
word  is  put  for  the  effect  of  this  cause,  in  producing 
velocity,  or  in  producing  motion  towards  that  centre. 

Heat  signifies  a  sensation,  and  cold  a  contrary  one; 
but  heat  likewise  signifies  a  quality  or  state  of  bodies, 
which  hath  no  contrary,  but  different  degrees.  When  a 
man  feels  the  same  water  hot  to  one  hand  and  cold  to 
the  other,  this  gives  him  occasion  to  distinguish  between 
the  feeling  and  the  heat  of  the  body;  and,  although  he 
knows  that  the  sensations  are  contrary,  he  does  not 
imagine  that  the  body  can  have  contrary  qualities  at  the 
same  time.  And  when  he  finds  a  different  taste  in  the 
same  body  in  sickness  and  in  health,  he  is  easily  con- 
vinced, that  the  quality  in  the  body  called  taste  is  the 
same  as  before,  although  the  sensations  he  has  from  it 
are  perhaps  opposite. 

The  vulgar  are  commonly  charged  by  philosophers, 
with  the  absurdity  of  imagining  the  smell  in  the  rose  to 
be  something  like  to  the  sensation  of  smelling;  but  I 
think  unjustly;  for  they  neither  give  the  same  epithets 
to  both,  nor  do  they  reason  in  the  same  manner  from 
them.  What  is  smell  in  the  rose  ?  It  is  a  quality  or  vir- 
tue of  the  rose,  or  of  something  proceeding  from  it, 
which  we  perceive  by  the  sense  of  smelling;  and  this  is 
all  we  know  of  the  matter.  But  what  is  smelling  ?  It 
is  an  act  of  the  mind,  but  is  never  imagined  to  be  a  qual- 
ity of  the  mind.  Again,  the  sensation  of  smelling  is  con- 
ceived to  infer  necessarily  a  mind  or  sentient  being;  but 
smell  in  the  rose  infers  no  such  thing.  We  say,  this 
body  smells  sweet,  that  stinks;  but  we  do  not  say,  this 
mind  smells,  sweet  and  that  stinks.  Therefore,  smell  in 


SEC.  IX]  THE  PHILOSOPHY  OF  REID.  115 

the  rose,  and  the  sensation  which  it  causes,  are  not  con- 
ceived, even  by  the  vulgar,  to  be  things  of  the  same 
kind,  although  they  have  the  same  name. 

From  what  hath  been  said,  we  may  learn  that  the 
smell  of  a  rose  signifies  two  things:  First,  a  sensation, 
which  can  have  no  existence  but  when  it  is  perceived, 
and  can  only  be  in  a  sentient  being  or  mind;  Secondly, 
it  signifies  some  power,  quality,  or  virtue,  in  the  rose,  or 
in  effluvia  proceeding  from  it,  which  hath  a  permanent 
existence,  independent  of  the  mind,  and  which,  by  the 
constitution  of  nature,  produces  the  sensation  in  us.  By 
the  original  constitution  of  our  nature,  we  are  both  led 
to  believe  that  there  is  a  permanent  cause  of  the  sensa- 
tion, and  prompted  to  seek  after  it;  and  experience  de- 
termines us  to  place  it  in  the  rose.  The  names  of  all 
smells,  tastes,  sounds,  as  well  as  heat  and  cold,  have  a 
like  ambiguity  in  all  languages;  but  it  deserves  our  at- 
tention, that  these  names  are  but  rarely,  in  common  lan- 
guage, used  to  signify  the  sensations;  for  the  most  part, 
they  signify  the  external  qualities  which  are  indicated  by 
the  sensations — the  cause  of  which  phenomenon  I  take 
to  be  this.  Our  sensations  have  very  different  degrees  of 
strength.  Some  of  them  are  so  quick  and  lively  as  to 
give  us  a  great  deal  either  of  pleasure  or  of  uneasiness. 
When  this  is  the  case,  we  are  compelled  to  attend  to  the 
sensation  itself,  and  to  make  it  an  object  of  thoughf  and 
discourse;  we  give  it  a  name,  which  signifies  nothing  but 
the  sensation;  and  in  this  case  we  readily  acknowledge, 
that  the  thing  meant  by  that  name  is  in  the  mind  only, 
and  not  in  anything  external.  Such  are  the  various  kinds 
of  pain,  sickness,  and  the  sensations  of  hunger  and  other 
appetites.  But,  where  the  sensation  is  not  so  interesting 
as  to  require  to  be  made  an  object  of  thought,  our  con- 
stitution leads  us  to  consider  it  as  a  sign  of  something 
external,  which  hath  a  constant  conjunction  with  it;  and, 
having  found  what  it  indicates,  we  give  a  name  to  that: 
the  sensation,  having  no  proper  name,  falls  in  as  an  ac- 


Il6  THE  PHILOSOPHY   OF  REID.  [Cn.  II. 

cessory  to  the  thing  signified  by  it,  and  is  confounded 
under  the  same  name.  So  that  the  name  may,  indeed, 
be  applied  to  the  sensation,  but  most  properly  and  com- 
monly is  applied  to  the  thing  indicated  by  that  sensation. 
The  sensations  of  smell,  taste,  sound,  and  colour,  are  of 
infinitely  more  importance  as  signs  or  indications,  than 
they  are  upon  their  own  account;  like  the  words  of  a 
language,  wherein  we  do  not  attend  to  the  sound  but  to 
the  sense. 

Section  X. 

WHETHER  IN  SENSATION  THE  MIND  IS  ACTIVE  OR  PASSIVE  ? 

There  is  one  inquiry  remains,  Whether,  in  smelling, 
and  in  other  sensations,  the  mind  is  active  or  passive  ? 
This  possibly  may  seem  to  be  a  question  about  words, 
or,  at  least,  of  very  small  importance;  however,  if  it  leads 
us  to  attend  more  accurately  to  the  operations  of  our 
minds  than  we  are  accustomed  to  do,  it  is,  upon  that 
very  account,  not  altogether  unprofitable.  I  think  the 
opinion  of  modern  philosophers  is,  that  in  sensation  the 
mind  is  altogether  passive.*  And  this  undoubtedly  is 
so  far  true,  that  we  cannot  raise  any  sensation  in  our 
minds  by  willing  it;  and,  on  the  other  hand,  it  seems 
hardly  possible  to  avoid  having  the  sensation  when  the 
object  is  presented.  Yet  it  seems  likewise  to  be  true, 
that,  in  proportion  as  the  attention  is  more  or  less  turned 
to  a  sensation  or  diverted  from  it,  that  sensation  is  more 
or  less  perceived  and  remembered.  Every  one  knows 
that  very  intense  pain  may  be  diverted  by  a  surprise,  or  by 
anything  that  entirely  occupies  the  mind.  When  we 
are  engaged  in  earnest  conversation,  the  clock  may 
strike  by  us  without  being  heard;  at  least,  we  remember 
not,  the  next  moment,  that  we  did  hear  it.  The  noise 
and  tumult  of  a  great  trading  city  is  not  heard  by  them 
who  have  lived  in  it  all  their  days;  but  it  stuns  those 
\  strangers  who  have  lived  in  the  peaceful  retirement  of  the 

*  This  is  far  too  absolutely  stated — H, 


SEC.  X.]  THE  PHILOSOPHY   OF  REID.  117 

country.  Whether,  therefore,  there  can  be  any  sensation 
where  the  mind  is  purely  passive,  I  will  not  say;  but  I  think 
we  are  conscious  of  having  given  some  attention  to  every 
sensation  which  we  remember,  though  ever  so  recent 

No  doubt,  where  the  impulse  is  strong  and  uncom- 
mon, it  is  as  difficult  to  withhold  attention  as  it  is  to 
forbear  crying  out  in  racking  pain,  or  starting  in  a  sud- 
den fright.  But  how  far  both  might  be  attained  by 

v  strong  resolution  and  practice,  is  not  easy  to  determine. 
So  that,  although  the  Peripatetics  had  no  good  reason  to 
suppose  an  active  and  a  passive  intellect,  since  attention 
may  be  well  enough  accounted  an  act  of  the  will,  yet  I 
think  they  came  nearer  to  the  truth,  in  holding  the  mind 

\  to  be  in  sensation  partly  passive  and  partly  active,  than 
the  moderns  in  affirming  it  to  be  purely  passive.  Sensa- 
tion, imagination,  memory  and  judgment,  have,  by  the 
vulgar  in  all  ages,  been  considered  as  acts  of  the  mind. 

\  The  manner  in  which  they  are  expressed  in  all  languages, 
shews  this.  When  the  mind  is  much  employed  in  them, 
we  say  it  is  very  active;  whereas,  if  they  were  impressions 
only,  as  the  ideal  philosophy  would  lead  us  to  conceive, 
we  ought,  in  such  a  case,  rather  to  say,  that  the  mind  is 
very  passive;  for,  I  suppose,  no  man  would  attribute 
great  activity  to  the  paper  I  write  upon,  because  it  re- 
ceives variety  of  characters. 

The  relation  which  the  sensation  of  smell  bears  to  the 
memory  and  imagination  of  it,  and  to  a  mind  or  subject, 
is  common  to  all  our  sensations,  and,  indeed,  to  all  the 
operations  of  the  mind:  the  relation  it  bears  to  the  will 
is  common  to  it  with  all  the  powers  of  understanding: 
and  the  relation  it  bears  to  that  quality  or  virtue  of 
bodies  which  it  indicates,  is  common  to  it  with  the  sen- 
sations of  taste,  hearing,  colour,  heat,  and  cold — so  that 
what  hath  been  said  of  this  sense,  may  easily  be  applied 
to  several  of  our  senses,  and  to  other  operations  of  the 
mind;  and  this,  I  hope,  will  apologize  for  our  insisting 
so  long  upon  it. 


Il8  THE  PHILOSOPHY  OF  REID.  [Cu.  III. 

CHAPTER  III. 
OF  TASTING. 

A  GREAT  part  of  what  hath  been  said  of  the  sense  of 
smelling,  is  so  easily  applied  to  those  of  tasting  and 
hearing,  that  we  shall  leave  the  application  entirely  to 
the  reader's  judgment,  and  save  ourselves  the  trouble 
of  a  tedious  repetition. 

It  is  probable  that  everything  that  affects  the  taste  is, 
in  some  degree,  soluble  in  the  saliva.  It  is  not  con- 
ceivable how  any  thing  should  enter  readily,  and  of  its 
own  accord,  as  it  were,  into  the  pores  of  the  tongue, 
palate,  and  fauces,  unless  it  had  some  chemical  affinity 
to  that  liquor  with  which  these  pores  are  always  replete. 
It  is,  therefore,  an  admirable  contrivance  of  nature,  that 

\^  the  organs  of  taste  should  always  be  moist  with  a  liquor 
which  is  so  universal  a  menstruum,  and  which  deserves 
to  be  examined  more  than  it  hath  been  hitherto,  both  in 

v  that  capacity,  and  as  a  medical  unguent.  Nature 
teaches  dogs,  and  other  animals,  to  use  it  in  this  last 
way;  and  its  subserviency  both  to  taste  and  digestion 
shews  its  efficacy  in  the  former. 

It  is  with  manifest  design  and  propriety,  that  the  or- 
gan of  this  sense  guards  the  entrance  of  the  alimentary 
canal,  as  that  of  smell  the  entrance  of  the  canal  for 
respiration.  And  from  these  organs  being  placed  in  such 
manner  that  everything  that  enters  into  the  stomach 
must  undergo  the  scrutiny  of  both  senses,  it  is  plain  that 
they  were  intended  by  nature  to  distinguish  wholesome 
food  from  that  which  is  noxious.  The  brutes  have  no 

^  other  means  of  choosing  their  food;  nor  would  mankind, 
in  the  savage  state.  And  it  is  very  probable  that  the 
smell  and  taste,  noway  vitiated  by  luxury  or  bad  habits, 


CH.  III.]  THE  PHILOSOPHY  OF  REID.  119 

would  rarely,  if  ever,  lead  us  to  a  wrong  choice  of  food 
among  the  productions  of  nature;  although  the  artificial 
compositions  of  a  refined  and  luxurious  cookery,  or  of 
chemistry  and  pharmacy,  may  often  impose  upon  both, 
and  produce  things  agreeable  to  the  taste  and  smell, 
which  are  noxious  to  health.  And  it  is  probable  that 
both  smell  and  taste  are  vitiated,  and  rendered  less  fit  to 
perform  their  natural  offices,  by  the  unnatural  kind  of 
life  men  commonly  lead  in  society. 

These  senses  are  likewise  of  great  use  to  distinguish 
bodies  that  cannot  be  distinguished  by  our  other  senses, 
and  to  discern  the  changes  which  the  same  body  under- 
goes, which,  in  many  cases,  are  sooner  perceived  by 
taste  and  smell  than  by  any  other  means.  How  many 
things  are  there  in  the  market,  the  eating-house,  and  the 
tavern,  as  well  as  in  the  apothecary  and  chemist's  shops, 
which  are  known  to  be  what  they  are  ^given  out  to  be, 
and  are  perceived  to  be  good  or  bad  in  their  kind,  only 
by  taste  or  smell  ?  And  how  far  our  judgment  of  things, 
by  means  of  our  senses,  might  be  improved  by  accurate 
attention  to  the  small  differences  of  taste  and  smell,  and 
other  sensible  qualities,  is  not  easy  to  determine.  Sir 
Isaac  Newton,  by  a  noble  effort  of  his  great  genius,  at- 
tempted, from  the  colour  of  opaque  bodies,  to  discover 
the  magnitude  of  the  minute  pellucid  parts  of  which  they 
are  compounded:  and  who  knows  what  new  lights  nat- 
ural philosophy  may  yet  receive  from  other  secondary 
qualities  duly  examined  ? 

Some  tastes  and  smells  stimulate  the  nerves  and  raise 
the  spirits:  but  such  an  artificial  elevation  of  the  spirits 
is,  by  the  laws  of  nature,  followed  by  a  depression, 
which  can  only  be  relieved  by  time,  or  by  the  repeated 
use  of  the  like  stimulus.  By  the  use  of  such  things  we 
create  an  appetite  for  them,  which  very  much  resembles, 
and  hath  all  the  force  of  a  natural  one.  It  is  in  this 
manner  that  men  acquire  an  appetite  for  snuff,  tobacco, 
strong  liquors,  laudanum,  and  the  like. 


120  THE  PHILOSOPHY   OF  REID.  [Cn.  III. 

Nature,  indeed,  seems  studiously  to  have  set  bounds 
to  the  pleasures  and  pains  we  have  by  these  two  senses, 
and  to  have  confined  them  within  very  narrow  limits, 
that  we  might  not  place  any  part  of  our  happiness  in 
them;  there  being  hardly  any  smell  or  taste  so  disagree- 
able that  use  will  not  make  it  tolerable,  and  at  last  per- 
haps agreeable,  nor  any  so  agreeable  as  not  to  lose  its 
relish  by  constant  use.  Neither  is  there  any  pleasure  or 
pain  of  these  senses  which  is  not  introduced  or  followed 
by  some  degree  of  its  contrary,  which  nearly  balances  it; 
so  that  we  may  here  apply  the  beautiful  allegory  of  the 
divine  Socrates — that,  although  pleasure  and  pain  are 
contrary  in  their  nature,  and  their  faces  look  different 
ways,  yet  Jupiter  hath  tied  them  so  together  that  he  that 
lays  hold  of  the  one  draws  the  other  along  with  it 

As  there  is  a  great  variety  of  smells,  seemingly  simple 
and  uncompounded,  not  only  altogether  unlike,  but 
some  of  them  contrary  to  others,  and  as  the  same  thing 
may  be  said  of  tastes,  it  would  seem  that  one  taste  is  not 
less  different  from  another  than  it  is  from  a  smell  :  and 
therefore  it  may  be  a  question,  how  all  smells  come 
to  be  considered  as  one  genus,  and  all  tastes  as 
another  ?  What  is  the  generical  distinction  ?  Is  it 
only  that  the  nose  is  the  organ  of  the  one  and  the  pal- 
ate of  the  other  ?  or,  abstracting  from  the  organ,  is  there 
not  in  the  sensations  themselves  something  common  to 
smells,  and  something  else  common  to  tastes,  whereby 
the  one  is  distinguished  from  the  other?  It  seems  most 
probable  that  the  latter  is  the  case;  and  that,  under  the 
appearance  of  the  greatest  simplicity,  there  is  still  in 
these  sensations  something  of  composition. 

If  one  considers  the  matter  abstractly,  it  would  seem 
that  a  number  of  sensations,  or,  indeed,  of  any  other 
individual  things,  which  are  perfectly  simple  and  uncom- 
pounded, are  incapable  of  being  reduced  into  genera  and 
species;  because  individuals  which  belong  to  a  species 
must  have  something  peculiar  to  each,  by  which  they 


CH.  III.]  THE  PHILOSOPHY  OF  REID.  121 

are  distinguished,  and  something  common  to  the  whole 
species.  And  the  same  may  be  said  of  species  which  be- 
long to  one  genus.  And,  whether  this  does  not  imply 
some  kind  of  composition,  we  shall  leave  to  -metaphy- 
sicians to  determine. 

The  sensations  both  of  smell  and  taste  do  undoubtedly 
admit  of  an  immense  variety  of  modifications,  which  no 
language  can  express.  If  a  man  was  to  examine  five 
hundred  different  wines,  he  would  hardly  find  two  of 
them  that  had  precisely  the  same  taste.  The  same  thing 
holds  in  cheese,  and  in  many  other  things.  Yet,  of  five 
hundred  different  tastes  in  cheese  or  wine,  we  can  hardly 
describe  twenty,  so  as  to  give  a  distinct  notion  of  them 
to  one  who  had  not  tasted  them. 

Dr.  Nehemiah  Grew,  a  most  judicious  and  laborious 
naturalist,  in  a  discourse  read  before  the  Royal  Society, 
anno  1675,  ^atn  endeavoured  to  shew  that  there  are  at 
least  sixteen  different  simple  tastes,  which  he  enumerates. 
How  many  compounded  ones  may  be  made  out  of  all 
the  various  combinations  of  two,  three,  four,  or  more 
of  these  simple  ones,  they  who  are  acquainted  with  the 
theory  of  combinations  will  easily  perceive.  All  these 
have  various  degrees  of  intenseness  and  weakness. 
Many  of  them  have  other  varieties;  in  some  the  taste  is 
more  quickly  perceived  upon  the  application  of  the  sapid 
body,  in  others  more  slowly — in  some  the  sensation  is 
more  permanent,  in  others  more  transient — in  some  it 
seems  to  undulate  or  return  after  certain  intervals,  in 
others  it  is  constant:  the  various  parts  of  the  organ — as 
the  lips,  the  tip  of  the  tongue,  the  root  of  the  tongue, 
the  fauces,  the  uvula,  and  the  throat — are  some  of  them 
chiefly  affected  by  one  sapid  body,  and  others  by  an- 
other. All  these,  and  other  varieties  of  tastes,  that  ac- 
curate writer  illustrates  by  a  number  of  examples. 
Nor  is  it  to  be  doubted,  but  smells,  if  examined  with 
the  same  accuracy,  would  appear  to  have  as  great  variety. 


122  THE  PHILOSOPHY  OF  REID.  [CH.  IV. 


CHAPTER   IV. 

OF  HEARING. 

Section  Z 

VARIETY  OF  SOUNDS — THEIR  PLACE   AND    DISTANCE    LEARNED 
BY    CUSTOM,    WITHOUT   REASONING. 

SOUNDS  have  probably  no  less  variety  of  modifications, 
than  either  tastes  or  odours.  For,  first,  sounds  differ  in 
tone.  The  ear  is  capable  of  perceiving  four  or  five  hun- 
dred variations  of  tone  in  sound,  and  probably  as  many 
different  degrees  of  strength;  by  combining  these,  we 
have  above  twenty  thousand  simple  sounds  that  differ 
either  in  tone  or  strength,  supposing  every  tone  to  be 
perfect.  But  it  is  to  be  observed,  that  to  make  a  perfect 
tone,  a  great  many  undulations  of  elastic  air  are  required, 
which  must  all  be  of  equal  duration  and  extent,  and  fol- 
low one  another  with  perfect  regularity;  and  each  undu- 
lation must  be  made  up  of  the  advance  and  recoil  of  in- 
numerable particles  of  elastic  air,  whose  motions  are  all 
uniform  in  direction,  force,  and  time.  Hence  we  may 
easily  conceive  a  prodigious  variety  in  the  same  tone, 
arising  from  irregularities  of  it,  occasioned  by  the  con- 
stitution, figure,  situation,  or  manner  of  striking  the  sono- 
rous body;  from  the  constitution  Of  the  elastic  medium, 
or  its  being  disturbed  by  other  motions;  and  from  the 
constitution  of  the  ear  itself,  upon  which  the  impres- 
sion is  made. 

A  flute,  a  violin,  a  hautboy,  and  a  French  horn,  may 
all  sound  the  same  tone  and  be  easily  distinguishable. 
Nay,  if  twenty  human  voices  sound  the  same  note,  and 
with  equal  strength,  there  will  still  be  some  difference. 


SEC.  I.]  THE  PHILOSOPHY  OF  REID.  l±3 

The  same  voice,  while  it  retains  its  proper  distinctions, 
may  yet  be  varied  many  ways,  by  sickness  or  health, 
youth  or  age,  leanness  or  fatness,  good  or  bad  humour. 
The  same  words  spoken  by  foreigners  and  natives — nay, 
by  persons  of  different  provinces  of  the  same  nation — 
may  be  distinguished. 

Such  an  immense  variety  of  sensations  of  smell,  taste, 
and  sound,  surely  was  not  given  us  in  vain.  They  are 
signs  by  which  we  know  and  distinguish  things  without 
us;  and  it  was  fit  that  the  variety  of  the  signs  should,  in 
some  degree,  correspond  with  the  variety  of  the  things 
signified  by  them. 

It  seems  to  be  by  custom  that  we  learn  to  distinguish 
both  the  place  of  things,  and  their  nature,  by  means  of 
their  sound.  That  such  a  noise  is  in  the  street,  such 
another  in  the  room  above  me;  that  this  is  a  knock  at 
my  door,  that  a  person  walking  up  stairs — is  probably 
learnt  by  experience.  I  remember,  that  once  lying  abed, 
and  having  been  put  into  a  fright,  I  heard  my  own  heart 
beat;  but  I  took  it  to  be  one  knocking  at  the  door,  and 
arose  and  opened  the  door  oftener  than  once,  before  I 
discovered  that  the  sound  was  in  my  own  breast.  It  is 
probable,  that,  previous  to  all  experience,  we  should  as 
little  know  whether  a  sound  came  from  the  right  or  left, 
from  above  or  below,  from  a  great  or  a  small  distance, 
as  we  should  know  whether  it  was  the  sound  of  a  drum, 
or  a  bell,  or  a  cart.  Nature  is  frugal  in  her  operations, 
and  will  not  be  at  the  expense  of  a  particular  instinct,  to 
give  us  that  knowledge  which  experience  will  soon 
produce,  by  means  of  a  general  principle  of  human 
nature. 

For  a  little  experience,  by  the  constitution  of  human 
nature,  ties  together,  not  only  in  our  imagination,  but  in 
our  belief,  those  things  which  were  in  their  nature  un- 
connected. When  I  hear  a  certain  sound,  I  conclude 
immediately,  without  reasoning,  that  a  coach  passes  by. 
There  are  no  premises  from  which  this  conclusion  is  in- 


124  THE  PHILOSOPHY   OF   REID.  [Cn.  IV. 

ferred  by  any  rules  of  logic.     It  is  the  effect  of  a  princi- 
ple of  our  nature,  common  to  us  with  the  brutes. 

Although  it  is  by  hearing  that  we  are  capable  of  the 
perceptions  of  harmony  and  melody,  and  of  all  the  charms 
of  music,  yet  it  would  seem  that  these  require  a  higher 
faculty,  which  we  call  a  musical  ear.  This  seems  to  be 
in  very  different  degrees,  in  those  who  have  the  bare  fac- 
ulty of  hearing  equally  perfect;  and,  therefore,  ought  not 
to  be  classed  with  the  external  senses,  but  in  a  higher 
order. 

Section  II. 

OF  NATURAL  LANGUAGE. 

One  of  the  noblest  purposes  of  sound  undoubtedly  is 
language,  without  which  mankind  would  hardly  be  able 
to  attain  any  degree  of  improvement  above  the  brutes. 
Language  is  commonly  considered  as  purely  an  inven- 
tion of  men,  who  by  nature  are  no  less  mute  than  the 
brutes;  but,  having  a  superior  degree  of  invention  and 
reason,  have  been  able  to  contrive  artificial  signs  of  their 
thoughts  and  purposes,  and  to  establish  them  by  com- 
mon consent.  But  the  origin  of  language  deserves  to  be 
more  carefully  inquired  into,  not  only  as  this  inquiry 
may  be  of  importance  for  the  improvement  of  language, 
but  as  it  is  related  to  the  present  subject,  and  tends  to 
lay  open  some  of  the  first  principles  of  human  nature. 
I  shall,  therefore,  offer  some  thoughts  upon  this  sub- 
ject. 

By  language  I  understand  all  those  signs  which  man- 
kind use  in  order  to  communicate  to  others  their 
thoughts  and  intentions,  their  purposes  and  desires. 
And  such  signs  may  be  conceived  to  be  of  two  kinds: 
First,  such  as  have  no  meaning  but  what  is  affixed  to 
them  by  compact  or  agreement  among  those  who  use 
them — these  are  artificial  signs;  Secondly,  such  as,  previ- 
ous to  all  compact  or  agreement,  have  a  meaning  which 


SEC.  II.]  THE  PHILOSOPHY   OF  REID.  125 

every  man  understands  by  the  principles  of  his  nature. 
Language,  so  far  as  it  consists  of  artificial  signs,  may  be 
called  artificial;  so  far  as  it  consists  of  natural  signs,  I 
call  it  natural. 

Having  premised  these  definitions,  I  think  it  is  de- 
monstrable, that,  if  mankind  had  not  a  natural  lan- 
guage they  could  never  have  invented  an  artificial  one  by 
their  reason  and  ingenuity.  For  all  artificial  language 
supposes  some  compact  or  agreement  to  affix  a  certain 
meaning  to  certain  signs;  therefore,  there  must  be  com- 
pacts or  agreements  before  the  use  of  artificial  signs;  but 
there  can  be  no  compact  or  agreement  without  signs,  nor 
without  language;  and,  therefore,  there  must  be  a  natu- 
/  ral  language  before  any  artificial  language  can  be  in- 
vented: which  was  to  be  demonstrated. 

Had  language  in  general  been  a  human  invention,  as 
much  as  writing  or  printing,  we  should  find  whole  na- 
tions as  mute  as  the  brutes.  Indeed,  even  the  brutes 
have  some  natural  signs  by  which  they  express  their  own 
thoughts,  affections,  and  desires,  and  understand  those 
of  others.  A  chick,  as  soon  as  hatched,  understands  the 
different  sounds  whereby  its  dam  calls  it  to  food,  or 
gives  the  alarm  of  danger.  A  dog  or  a  horse  under- 
stands, by  nature,  when  the  human  voice  caresses,  and 
when  it  threatens  him.  But  brutes,  as  far  as  we  know, 
have  no  notion  of  contracts  or  covenants,  or  of  moral 
obligation  to  perform  them.  If  nature  had  given  them 
these  notions,  she  would  probably  have  given  them  nat- 
ural signs  to  express  them.  And  where  nature  has  de- 
nied these  notions,  it  is  as  impossible  to  acquire  them  by 
art,  as  it  is  for  a  blind  man  to  acquire  the  notion  of  col- 
ours. Some  brutes  are  sensible  of  honour  or  disgrace;  they 
have  resentment  and  gratitude;  but  none  of  them,  as  far 
as  we  know,  can  make  a  promise  or  plight  their  faith, 
having  no  such  notions  from  their  constitution.  And 
if  mankind  had  not  these  notions  by  nature,  and 
natural  signs  to  express  them  by,  with  all  their  wit 


126  THE  PHILOSOPHY   OF   REID.  [Cn.  IV. 

and  ingenuity  they  could  never  have  invented  lan- 
guage. 

The  elements  of  this  natural  language  of  mankind,  or 
the  signs  that  are  naturally  expressive  of  our  thoughts, 
may,  I  think,  be  reduced  to  these  three  kinds:  modula- 
tions of  the  voice,  gestures,  and  features.  By  means  of 
these,  two  savages  who  have  no  common  artificial  lan- 
guage, can  converse  together,  can  communicate  their 
thoughts  in  some  tolerable  manner;  can  ask  and  refuse, 
affirm  and  deny,  threaten  and  supplicate;  can  traffic, 
enter  into  covenants,  and  plight  their  faith.  This  might 
be  confirmed  by  historical  facts  of  undoubted  credit,  if 
it  were  necessary. 

Mankind  having  thus  a  common  language  by  nature, 
though  a  scanty  one,  adapted  only  to  the  necessities  of 
nature,  there  is  no  great  ingenuity  required  in  improving 
it  by  the  addition  of  artificial  signs,  to  supply  the  deficiency 
of  the  natural.  These  artificial  signs  must  multiply  with 
the  arts  of  life,  and  the  improvements  of  knowledge.  The 
articulations  of  the  voice  seem  to  be,  of  all  signs,  the 
most  proper  for  artificial  language;  and  as  mankind  have 
universally  used  them  for  that  purpose,  we  may  reason- 
ably judge  that  nature  intended  them  for  it.'  But  nature 
probably  does  not  intend  that  we  should  lay  aside  the 
use  of  the  natural  signs;  it  is  enough  that  we  supply  their 
defects  by  artificial  ones.  A  man  that  rides  always  in  a 
chariot,  by  degrees  loses  the  use  of  his  legs;  and  one  who 
uses  artificial  signs  only,  loses  both  the  knowledge  and 
use  of  the  natural.  Dumb  people  retain  much  more 
of  the  natural  language  than  others,  because  necessity 
obliges  them  to  use  it.  And  for  the  same  reason,  sav- 
ages have  much  more  of  it  than  civilized  nations.  It  is 
by  natural  signs  chiefly  that  we  give  force  and  energy  to 
language;  and  the  less  language  has  of  them,  it  is  the 
less  expressive  and  persuasive.  Thus,  writing  is  less  ex- 
pressive than  reading,  and  reading  less  expressive 
than  speaking  without  book ;,  speaking  without  the 


SEC.  II.]  THE  PHILOSOPHY  OF  REID.  127 

proper  and  natural  modulations,  force,  and  variations  of 
the  voice,  is  a  frigid  and  dead  language,  compared  with 
that  which  is  attended  with  them;  it  is  still  more  express- 
ive when  we  add  the  language  of  the  eyes  and  features; 
and  is  then  only  in  its  perfect  and  natural  state,  and  at- 
tended with  its  proper  energy,  when  to  all  these  we 
superadd  the  force  of  action. 

Where  speech  is  natural,  it  will  be  an  exercise,  not  of 
the  voice  and  lungs  only,  but  of  all  the  muscles  of  the 
body;  like  that  of  dumb  people  and  savages,  whose  lan- 
guage, as  it  has  more  of  nature,  is  more  expressive,  and 
is  more  easily  learned. 

Is  it  not  pity  that  the  refinements  of  a  civilized  life,  in- 
stead of  supplying  the  defects  of  natural  language,  should 
root  it  out  and  plant  in  its  stead  dull  and  lifeless  articu- 
lations of  unmeaning  sounds,  or  the  scrawling  of  insig- 
nificant characters  ?  The  perfection  of  language  is  com- 
monly thought  to  be,  to  express  human  thoughts  and 
sentiments  distinctly  by  these  dull  signs;  but  if  this  is 
the  perfection  of  artificial  language,  it  is  surely  the.  cor- 
ruption of  the  natural. 

Artificial  signs  signify,  but  they  do  not  express;  they 
speak  to  the  understanding,  as  algebraical  characters 
may  do,  but  the  passions,  the  affections,  and  the  will, 
hear  them  not;  these  continue  dormant  and  inactive, 
till  we  speak  to  them  in  the  language  of  nature,  to  which 
they  are  all  attention  and  obedience. 

It  were  easy  to  show,  that  the  fine  arts  of  the  musician, 
the  painter,  the  actor,  and  the  orator,  so  far  as  they  are 
expressive — although  the  knowledge  of  them  requires  in 
us  a  delicate  taste,  a  nice  judgment,  and  much  study 
and  practice — yet  they  are  nothing  else  but  the  language 
of  nature,  which  we  brought  into  the  world  with  us,  but 
have  unlearned  by  disuse,  and  so  find  the  greatest  diffi- 
culty in  recovering  it. 

Abolish  the  use  of  articulate  sounds  and  writing 
among  mankind  for  a  century,  and  every  man  would  be  a 


128  THE  PHILOSOPHY  OF  REID.        [Cn.  IV.,  SEC.  II. 

painter,  an  actor,  and  an  orator.  We  mean  not  to 
affirm  that  such  an  expedient  is  practicable;  or,  if  it  were, 
that  the  advantage  would  counterbalance  the  loss;  but 
that,  as  men  are  led  by  nature  and  necessity  to  converse 
together,  they  will  use  every  mean  in  their  power  to 
make  themselves  understood;  and  where  they  cannot  do 
this  by  artificial  signs,  they  will  do  it,  as  far  as  possible, 
by  natural  ones:  and  he  that  understands  perfectly  the 
use  of  natural  signs,  must  be  the  best  judge  in  all  the 
expressive  arts. 


CH.  V.,  SEC.  I.]  THE  PHILOSOPHY  OF  REID.  129 


CHAPTER  V. 

OF  TOUCH. 
Section  I. 

OF  HEAT  AND  COLD. 

THE  senses  which  we  have  hitherto  considered,  are 
very  simple  and  uniform,  each  of  them  exhibiting  only 
one  kind  of  sensation,  and  thereby  indicating  only  one 
quality  of  bodies.  By  the  ear  we  perceive  sounds,  and 
nothing  else;  by  the  palate,  tastes;  and  by  the  nose., 
odours.  These  qualities  are  all  likewise  of  one  order, 
being  all  secondary  qualities;  whereas,  by  touch  we 
perceive  not  one  quality  only,  but  many,  and  those 
of  very  different  kinds.  The  chief  of  them  are  heat  and 
cold,  hardness  and  softness,  roughness  and  smoothness, 
figure,  solidity,  motion,  and  extension.  We  shall  con- 
sider these  in  order. 

As  to  heat  and  cold,  it  will  easily  be  allowed  that  they 
are  secondary  qualities,  of  the  same  order  with  smell, 
taste,  and  sound.  And,  therefore,  what  hath  been 
already  said  of  smell,  is  easily  applicable  to  them;  that 
is,  that  the  words  heat  and  cold  have  each  of  them  two 
significations;  they  sometimes  signify  certain  sensations 
of  the  mind,  which  can  have  no  existence  when  they  are 
not  felt,  nor  can  exist  anywhere  but  in  a  mind  or  sen- 
tient being;  but  more  frequently  they  signify  a  quality  in 
bodies,  which,  by  the  laws  of  nature,  occasions  the  sen- 
sations of  heat  and  cold  in  us — a  quality  which,  though 
connected  by  custom  so  closely  with  the  sensation,  that 
we  cannot,  without  difficulty,  separate  them,  yet  hath  not 


130  THE  PHILOSOPHY   OF   REID.  [Cn.  V. 

the  least  resemblance  to  it,  and  may  continue  to  exist 
when  there  is  no  sensation  at  all. 

The  sensations  of  heat  and  cold  are  perfectly  known; 
for  they  neither  are,  nor  can  be,  anything  else  than  what 
we  feel  them  to  be;  but  the  qualities  in  bodies  which  we 
call-  heat  and  cold  are  unknown.  They  are  only  con- 
ceived by  us,  as  unknown  causes  or  occasions  of  the  sen- 
sations to  which  we  give  the  same  names.  But,  though 
common  sense  says  nothing  of  the  nature  of  these  quali- 
ties, it  plainly  dictates  the  existence  of  them;  and  to  deny 
that  there  can  be  heat  and  cold  when  they  are  not  felt, 
is  an  absurdity  too  gross  to  merit  confutation.  For 
what  could  be  more  absurd,  than  to  say,  that  the  ther- 
mometer cannot  rise  or  fall,  unless  some  person  be  pre- 
sent, or  that  the  coast  of  Guinea  would  be  as  cold  as 
Nova  Zembla,  if  it  had  no  inhabitants  ? 

It  is  the  business  of  philosophers  to  investigate,  by 
proper  experiments  and  induction,  what  heat  and  cold 
are  in  bodies.  And  whether  they  make  heat  a  particu- 
lar element  diffused  through  nature,  and  accumulated  in 
the  heated  body,  or  whether  they  make  it  a  certain  vi- 
bration of  the  parts  of  the  heated  body;  whether  they 
determine  that  heat  and  cold  are  contrary  qualities,  as 
the  sensations  undoubtedly  are  contrary,  or  that  heat 
only  is  a  quality,  and  cold  its  privation:  these  questions 
are  within  the  province  of  philosophy;  for  common  sense 
says  nothing  on  the  one  side  or  the  other. 

But,  whatever  be  the  nature  of  that  quality  in  bodies 
which  we  call  heat,  we  certainly  know  this,  that  it  can- 
not in  the  least  resemble  the  sensation  of  heat.  It  is  no 
less  absurd  to  suppose  a  likeness  between  the  sensation 
and  the  quality,  than  it  would  be  to  suppose  that  the 
pain  of  the  gout  resembles  a  square  or  a  triangle.  The 
simplest  man  that  hath  common  sense,  does  not  imagine 
the  sensation  of  heat,  or  anything  that  resembles  that 
sensation,  to  be  in  the  fire.  He  only  imagines  that  there 
is  something  in  the  fire  which  makes  him  and  other 


SEC.  II.]  THE  PHILOSOPHY   OF   REID.  13! 

sentient  beings  feel  heat.  Yet,  as  the  name  of  heat,  in 
common  language,  more  frequently  and  more  properly 
signifies  this  unknown  something  in  the  fire,  than  the 
sensation  occasioned  by  it,  he  justly  laughs  at  the  phi- 
losopher who  denies  that  there  is  any  heat  in  the  fire, 
and  thinks  that  he  speaks  contrary  to  common  sense. 

Section  II. 

OF   HARDNESS   AND   SOFTNESS. 

Let  us  next  consider  hardness  and  softness  ;  by  which 
words  we  always  understand  real  properties  or  qualities 
of  bodies  of  which  we  have  a  distinct  conception. 

When  the  parts  of  a  body  adhere  so  firmly  that  it 
cannot  easily  be  made  to  change  its  figure,  we  call  it 
hard  ;  when  its  parts  are  easily  displaced,  we  call  it  soft. 
This  is  the  notion  which  all  mankind  have  of  hardness 
and  softness  ;  they  are  neither  sensations,  nor  like  any 
sensation  ;  they  were  real  qualities  before  they  were  per- 
ceived by  touch,  and  continue  to  be  so  when  they  are 
not  perceived  ;  for  if  any  man  will  affirm  that  diamonds 
were  not  hard  tilf  they  were  handled,  who  would  reason 
with  him  ? 

There  is,  no  doubt,  a  sensation  by  which  we  perceive 
a  body  to  be  hard  or  soft  This  sensation  of  hardness 
may  easily  be  had,  by  pressing  one's  hand  against  the 
table,  and  attending  to  the  feeling  that  ensues,  setting 
aside,  as  much  as  possible,  all  thought  of  the  table  and 
its  qualities,  or  of  any  external  thing.  But  it  is  one 
thing  to  have  the  sensation,  and  another  to  attend  to  it, 
and  make  it  a  distinct  object  of  reflection.  The  first 
is  very  easy;  the  last,  in  most  cases,  extremely  difficult. 

We  are  so  accustomed  to  use  the  sensation  as  a  sign,  and 
to  pass  immediately  to  the  hardness  signified,  that,  as 
far  as  appears,  it  was  never  made  an  object  of  thought, 
either  by  the  vulgar  or  by  philosophers ;  nor  has  it  a 


132  THE  PHILOSOPHY   OF  REID.  [Cn.  V. 

name  in  any  language.  There  is  no  sensation  more  dis- 
tinct, or  more  frequent ;  yet  it  is  never  attended  to,  but 
passes  through  the  mind  instantaneously,  and  serves 
only  to  introduce  that  quality  in  bodies,  which,  by  a 
law  of  our  constitution,  it  suggests. 

There  are,  indeed,  some  cases,  wherein  it  is  no  difficult 
matter  to  attend  to  the  sensation  occasioned  by  the  hard- 
ness of  a  body  ;  for  instance,  when  it  is  so  violent  as  to 
occasion  considerable  pain  :  then  nature  calls  upon  us 
to  attend  to  it,  and  then  we  acknowledge  that  it  is  a  mere 
sensation,  and  can  only  be  in  a  sentient  being.  If  a  man 
runs  his  head  with  violence  against  a  pillar,  I  appeal  to 
him  whether  the  pain  he  feels  resembles  the  hardness  of 
the  stone,  or  if  he  can  conceive  anything  like  what  he 
feels  to  be  in  an  inanimate  piece  of  matter. 

The  attention  of  the  mind  is  here  entirely  turned 
towards  the  painful  feeling;  and,  to  speak  in  the  common 
language  of  mankind,  he  feels  nothing  in  the  stone,  but 
feels  a  violent  pain  in  his  head.  It  is  quite  otherwise 
when  he  leans  his  head  gently  against  the  pillar  ;  for 
then  he  will  tell  you  that  he  feels  nothing  in  his  head, 
but  feels  hardness  in  the  stone.  Hath  he  not  a  sensation 
in  this  case  as  well  as  in  the  other  ?  Undoubtedly  he  hath  ; 
but  it  is  a  sensation  which  nature  intended  only  as  a 
sign  of  something  in  the  stone  ;  and,  accordingly,  he 
instantly  fixes  his  attention  upon  the  thing  signified  ;  and 
cannot,  without  great  difficulty,  attend  so  much  to  the 
sensation  as  to  be  persuaded  that  there  is  any  such  thing 
distinct  from  the  hardness  it  signifies. 

But,  however  difficult  it  may  be  to  attend  to  this 
fugitive  sensation,  to  stop  its  rapid  progress,  and  to  dis- 
join it  from  the  external  quality  of  hardness,  in  whose 
shadow  it  is  apt  immediately  to  hide  itself ;  this  is  what 
a  philosopher  by  pains  and  practice  must  attain,  other- 
wise it  will  be  impossible  for  him  to  reason  justly  upon 
this  subject,  or  even  to  understand  what  is  here  advanced. 
For  the  last  appeal,  in  subjects  of  this  nature,  must 


SEC.  II.]  THE  PHILOSOPHY   OF  REID.  133 

be  to  what  a  man  feels  and  perceives  in  his  own 
mind. 

It  is  indeed  strange  that  a  sensation  which  we  have 
every  time  we  feel  a  body  hard,  and  which,  conse- 
quently, we  can  command  as  often  and  continue  as  long 
as  we  please,  a  sensation  as  distinct  and  determinate  as 
any  other,  should  yet  be  so  much  unknown  as  never  to 
have  been  made  an  object  of  thought  and  reflection,  nor 
to  have  been  honoured  with  a  name  in  any  language  : 
that  philosophers,  as  well  as  the  vulgar,  should  have 
entirely  overlooked  it,  or  confounded  it  with  that  quality 
of  bodies  which  we  call  hardness,  to  which  it  hath  not 
the  least  similitude.  May  we  not  hence  conclude,  that 
the  knowledge  of  the  human  faculties  is  but  in  its  in- 
fancy ? — that  we  have  not  yet  learned  to  attend  to  those 
operations  of  the  mind,  of  which  we  are  conscious  every 
hour  of  our  lives  ? — that  there  are  habits  of  inattention 
acquired  very  early,  which  are  as  hard  to  be  overcome 
as  other  habits  ?  For  I  think  it  is  probable,  that  the 
novelty  of  this  sensation  will  procure  some  attention 
to  it  in*  children  at  first ;  but,  being  in  nowise  interesting 
in  itself,  as  soon  as  it  becomes  familiar,  it  is  overlooked, 
and  the  attention  turned  solely  to  that  which  it  signifies. 
Thus,  when  one  is  learning  a  language,  he  attends  to  the 
sounds  ;  but  when  he  is  master  of  it,  he  attends  only  to 
the  sense  of  what  he  would  express.  If  this  is  the  case, 
we  must  become  as  little  children  again,  if  we  will  be 
philosophers  ;  we  must  overcome  this  habit  of  inattention 
which  has  been  gathering  strength  ever,  since  we  began 
to  think — a  habit,  the  usefulness  of  which,  in  common 
life,  atones  for  the  difficulty  it  creates  to  the  philosopher 
in  discovering  the  first  principles  of  the  human  mind. 

The  firm  cohesion  of  the  parts  of  a  body,  is  no  more 
like  that  sensation  by  which  I  perceive  it  to  be  hard,  than 
the  vibration  of  a  sonorous  body  is  like  the  sound  I  hear  : 
nor  can  I  possibly  perceive,  by  my  reason,  any  connec- 
tion between  the  one  and  the  other,  No  man  can  give 


134  THE  PHILOSOPHY   OF   REID.  [Cn.  V. 

a  reason,  why  the  vibration  of  a  body  might  not  have 
given  the  sensation  of  smelling,  and  the  effluvia  of  bodies 
affected  our  hearing,  if  it  had  so  pleased  our  Maker.  In 
like  manner,  no  man  can  give  a  reason  why  the  sen- 
sations of  smell,  or  taste,  or  sound,  might  not  have 
indicated  hardness,  as  well  as  that  sensation  which, 
by  our  constitution,  does  indicate  it.  Indeed,  no  man 
can  conceive  any  sensation  to  resemble  any  known 
quality  of  bodies.  Nor  can  any  man  show,  by  any  good 
argument,  that  all  our  sensations  might  not  have  been  as 
they  are,  though  no  body,  nor  quality  of  body,  had  ever 
existed. 

Here,  then,  is  a  phenomenon  of  human  nature,  which 
comes  to  be  resolved.  Hardness  of  bodies  is  a  thing 
that  we  conceive  as  distinctly,  and  believe  as  firmly,  as 
anything  in  nature.  We  have  no  way  of  coming  at  this 
conception  and  belief,  but  by  means  of  a  certain  sensa- 
tion of  touch,  to  which  hardness  hath  not  the  least  simil- 
itude; nor  can  we,  by  any  rules  of  reasoning,  infer  the 
one  from  the  other.  The  question  is,  How  we  come  by 
this  conception  and  belief? 

First,  as  to  the  conception:  Shall  we  call  it  an  idea  of 
sensation,  or  of  reflection  ?  The  last  will  not  be  affirmed; 
and  as  little  can  the  first,  unless  we  will  call  that  an  idea 
of  sensation  which  hath  no  resemblance  to  any  sensation. 
So  that  the  origin  of  this  idea  of  hardness,  one  of  the 
most  common  and  most  distinct  we  have,  is  not  to  be 
found  in  all  our  systems  of  the  mind:  not  even  in  those 
which  have  so  copiously  endeavoured  to  deduce  all  our 
notions  from  sensation  and  reflection. 

But,  secondly,  supposing  we  have  got  the  conception 
of  hardness,  how  come  we  by  the  belief  of  it  ?  Is  it  self- 
evident,  from  comparing  the  ideas,  that  such  a  sensation 
could  not  be  felt,  unless  such  a  quality  of  bodies  existed  ? 
No.  Can  it  be  proved  by  probable  or  certain  arguments  ? 
No;  it  cannot.  Have  we  got  this  belief,  then,  by  tradi- 
tion, by  education,  or  by  experience  ?  No;  it  is  not  got 


SEC.  III.]  THE  PHILOSOPHY   OF  REID.  135 

in  any  of  these  ways.  Shall  we  then  throw  off  this  be- 
lief as  having  no  foundation  in  reason  ?  Alas  !  it  is  not 
in  our  power;  it  triumphs  over  reason,  and  laughs  at  all 
the  arguments  of  a  philosopher.  Even  the  author  of  the 
"Treatise  of  Human  Nature,"  though  he  saw  no  reason 
for  this  belief,  but  many  against  it,  could  hardly  conquer 
it  in  his  speculative  and  solitary  moments;  at  other 
times,  he  fairly  yielded  to  it,  and  confesses  that  he  found 
himself  under  a  necessity  to  do  so. 

What  shall  we  say,  then,  of  this  conception,  and  this 
belief,  which  are  so  unaccountable  and  untractable  ?  I 
see  nothing  left,  but  to  conclude,  that,  by  an  original 
principle  of  our  constitution,  a  certain  sensation  of  touch 
both  suggests  to  the  mind  the  conception  of  hardness, 
and  creates  the  belief  of  it:  or,  in  other  words,  that  this 
sensation  is  a  natural  sign  of  hardness.  And  this  I 
shall  endeavour  more  fully  to  explain. 

Section  III. 

OF  NATURAL  SIGNS. 

As  in  artificial  signs  there  is  often  neither  similitude 
between  the  sign  and  thing  signified,  nor  any  connec- 
tion that  arises  necessarily  from  the  nature  of  the  things, 
so  it  is  also  in  natural  signs.  The  word  gold  has  no 
similitude  to  the  substance  signified  by  it;  nor  is  it  in 
its  own  nature  more  fit  to  signify  this  than  any  other  sub- 
stance; yet,  by  habit  and  custom,  it  suggests  this  and  no 
other.  In  like  manner,  a  sensation  of  touch  suggests 
hardness,  although  it  hath  neither  similitude  to  hardness, 
nor,  as  far  as  we  can  perceive,  any  necessary  connection 
with  it.  The  difference  betwixt  these  two  signs  lies  only 
in  this — that,  in  the  first,  the  suggestion  is  the  effect  of 
habit  and  custom;  in  the  second,  it  is  not  the  effect  of 
habit,  but  of  the  original  constitution  of  our  minds. 

It  appears  evident   from  what  hath  been  said   on  the 


136  THE  PHILOSOPHY  OF  REID.  [Cn.  V. 

subject  of  language,  that  there  are  natural  signs  as  well 
as  artificial;  and  particularly,  that  the  thoughts,  pur- 
poses, and  dispositions  of  the  mind,  have  their  natural 
signs  in  the  features  of  the  face,  the  modulation  of  the 
voice,  and  the  motion  and  attitude  of  the  body:  that, 
without  a  natural  knowledge  of  the  connection  between 
these  signs  and  the  things  signified  by  them,  language 
could  never  have  been  invented  and  established  among 
men:  and,  that  the  fine  arts  are  all  founded  upon  this 
connection,  which  we  may  call  the  natural  language  of 
mankind.  It  is  now  proper  to  observe,  that  there  are 
different  orders  of  natural  signs,  and  to  point  out  the 
different  classes  into  which  they  may  be  distinguished, 
that  we  may  more  distinctly  conceive  the  relation 
between  our  sensations  and  the  things  they  suggest,  and 
what  we  mean  by  calling  sensations  signs  of  external 
things. 

The  first  class  of  natural  signs  comprehends  those 
whose  connection  with  the  thing  signified  is  established 
by  nature,  but  discovered  only  by  experience.  The 
whole  of  genuine  philosophy  consists  in  discovering  such 
connections,  and  reducing  them  to  general  rules.  The 
great  Lord  Verulam  had  a  perfect  comprehension  of 
this,  when  he  called  it  an  interpretation  of  nature.  No 
man  ever  more  distinctly  understood  or  happily  ex- 
pressed the  nature  and  foundation  of  the  philosophic 
art.  What  is  all  we  know  of  mechanics,  astronomy,  and 
optics,  but  connections  established  by  nature,  and  dis- 
covered by  experience  or  observation,  and  consequences 
deduced  from  them  ?  All  the  knowledge  we  have  in  agri- 
culture, gardening,  chemistry,  and  medicine,  is  built 
upon  the  same  foundation.  And  if  ever  our  philosophy 
concerning  the  human  mind  is  carried  so  far  as  to  de- 
serve the  name  of  science,  which  ought  never  to  be  de- 
spaired of,  it  must  be  by  observing  facts,  reducing  them 
to  general  rules,  and  drawing  just  conclusions  from  them. 
What  we  commonly  call  natural  causes  might,  with  more 


.SEC.  III!]  THE  PHILOSOPHY  OF  REID.  137 

propriety,  be  called  natural  signs,  and  what  we  call 
effects,  the  things  signified.  The  causes  have  no  proper 
efficiency  or  causality,  as  far  as  we  know:  and  all  we  can 
certainly  affirm  is,  that  nature  hath  established  a  con- 
stant conjunction  between  them  and  the  things  called 
their  effects;  and  hath  given  to  mankind  a  disposition 
to  observe  those  connections,  to  confide  in  their  contin- 
uance, and  to  make  use  of  them  for  the  improvement  of 
our  knowledge,  and  increase  of  our  power. 

A  second  class  is  that  wherein  the  connection  between 
the  sign  and  thing  signified,  is  not  only  established  by 
nature,  but  discovered  to  us  by  a  natural  principle,  with- 
out reasoning  or  experience.  Of  this  kind  are  the  nat- 
ural signs  of  human  thoughts,  purposes,  and  desires, 
which  have  been  already  mentioned  as  the  natural  lan- 
guage of  mankind.  An  infant  may  be  put  into  a  fright 
by  an  angry  countenance,  and  soothed  again  by  smiles 
and  blandishments.  A  child  that  has  a  good  musical 
ear,  may  be  put  to  sleep  or  to  dance,  may  be  made  mer- 
ry or  sorrowful,  by  the  modulation  of  musical  ^sounds. 
The  principles  of  all  the  fine  arts,  and  of  what  we  call 
a  fine  taste,  may  be  resolved  into  connections  of  this 
kind.  A  fine  taste  may  be  improved  by  reasoning  and 
experience;  bur  if  the  first  principles  of  it  were  not 
planted  in  our  minds  by  nature,  it  could  never  be  ac- 
quired. Nay,  we  have  already  made  it  appear,  that  a 
great  part  of  this  knowledge  which  we  have  by  nature, 
is  lost  by  the  disuse  of  natural  signs,  and  the  substitution 
of  artificial  in  their  place. 

A  third  class  of  natural  signs  comprehends  those 
which,  though  we  never  before  had  any  notion  or  con- 
ception of  the  thing  signified,  do  suggest  it,  or  conjure 
it  up,  as  it  were,  by  a  natural  kind  of  magic,  and  at 
once  give  us  a  conception  and  create  a  belief  of  it.  I 
shewed  formerly,  that  our  sensations  suggest  to  us  a 
sentient  being  or  mind  to  which  they  belong — a  being 
which  hath  a  permanent  existence,  although  the  sensa- 


138  THE  PHILOSOPHY  OF  REID.  [Cn.  V. 

tions  are  transient  and  of  short  duration — a  being  which 
is  still  the  same,  while  its  sensations  and  other  operations 
are  varied  ten  thousand  ways — a  being  which  hath  the 
same  relation  to  all  that  infinite  variety  of  thoughts,  pur- 
poses, actions,  affections,  enjoyments,  and  sufferings, 
which  we  are  conscious  of,  or  can  remember.  The 
conception  of  a  mind  is  neither  an  idea  of  sensation  nor 
of  reflection;  for  it  is  neither  like  any  of  our  sensations, 
nor  like  anything  we  are  conscious  of.  The  first  con- 
ception of  it,  as  well  as  the  belief  of  it,  and  of  the  com- 
mon relation  it  bears  to  all  that  we  are  conscious  of,  or 
remember,  is  suggested  to  every  thinking  being,  we  do 
not  know  how. 

The  notion  of  hardness  in  bodies,  as  well  as  the  belief 
of  it,  are  got  in  a  similar  manner;  being,  by  an  original 
principle  of  our  nature,  annexed  to  that  sensation  which 
we  have  when  we  feel  a  hard  body.  And  so  naturally 
and  necessarily  does  the  sensation  convey  the  notion  and 
belief  of  hardness,  that  hitherto  they  have  been  con- 
founded by  the  most  acute  inquirers  into  the  principles 
of  human  nature,  although  they  appear,  upon  accurate 
reflection,  not  only  to  be  different  things,  but  as  unlike  as 
pain  is  to  the  point  of  a  sword. 

It  may  be  observed,  that,  as  the  first  class  of  natural 
signs  I  have  mentioned  is  the  foundation  of  true  philoso- 
phy, and  the  second  the  foundation  of  the  fine  arts,  or 
of  taste — so  the  last  is  the  foundation  of  common  sense 
— a  part  of  human  nature  which  hath  never  been  ex- 
plained. 

I  take  it  for  granted,  that  the  notion  of  hardness,  and 
the  belief  of  it,  is  first  got  by  means  of  that  particular 
sensation  which,  as  far  back  as  we  can  remember,  does 
invariably  suggest  it ;  and  that,  if  we  had  never  had  such 
a  feeling,  we  should  never  have  had  any  notion  of  hard- 
ness. I  think  it  is  evident,  that  we  cannot,  by  reasoning 
from  our  sensations,  collect  the  existence  of  bodies  at 
all,  far  less  any  of  their  qualities.  This  hath  been  proved 


SEC.  IV.]  THE   PHILOSOPHY   OF  REID.  139 

by  unanswerable  arguments  by  the  Bishop  of  Cloyne,  and 
by  the  author  of  the  "Treatise  of  Human  Nature."  It 
appears  as  evident  that  this  connection  between  our  sen- 
sations and  the  conception  and  belief  of  external  exist- 
ences cannot  be  produced  by  habit,  experience,  educa- 
tion, or  any  principle  of  human  nature  that  hath  been 
admitted  by  philosophers.  At  the  same  time,  it  is  a 
fact  that  such  sensations  are  invariably  connected  with 
the  conception  and  belief  of  external  existences.  Hence, 
by  all  rules  of  just  reasoning,  we  must  conclude  that  this 
connection  is  the  effect  of  our  constitution,  and  ought 
to  be  considered  as  an  original  principle  of  human 
nature,  till  we  find  some  more  general  principle  into 
which  it  may  be  resolved.  * 


Section  IV. 

OF    HARDNESS,    AND    OTHER   PRIMARY   QUALITIES. 

Further,  I  observe  that  hardness  is  a  quality,  of  which 
we  have  as  clear  and  distinct  a  conception  as  of  anything 
whatsoever.  The  cohesion  of  the  parts  of  a  body  with 
more  or  less  force,  is  perfectly  understood,  though  its 
cause  is  not ;  we  know  what  it  is,  as  well  as  how  it 
affects  the  touch.  It  is,  therefore,  a  quality  of  a  quite 
different  order  from  those  secondary  qualities  we  have 
already  taken  notice  of,  whereof  we  know  no  more  nat- 
urally than  that  they  are  adapted  to  raise  certain  sensa- 
tions in  us.  If  hardness  were  a  quality  of  the  same 
kind,  it  would  be  a  proper  inquiry  for  philosophers,  what 
hardness  in  bodies  is  ?  and  we  should  have  had  various 
hypotheses  about  it,  as  well  as  about  colour  and  heat. 

*  This  whole  doctrine  of  natural  signs,  on  which  his  philosophy 
is  in  a  great  measure  established,  was  borrowed  by  Reid,  in  principle, 
and  even  in  expression,  from  Berkeley.  Compare  "Minute  Philoso- 
pher," Dial.  IV.,  §§  7,  n,  12;  "New  Theory  of  Vision,"  §§  144. 
147;  "Theory  of  Vision  Vindicated,"  §§  38-43.— H. 


140  THE  PHILOSOPHY  OF  REID.  [Cn.  V. 

But  it  is  evident  that  any  such  hypothesis  would  be 
ridiculous.  If  any  man  should  say,  that  hardness  in 
bodies  is  a  certain  vibration  of  their  parts,  or  that  it  is 
certain  effluvia  emitted  by  them  which  affect  our  touch 
in  the  manner  we  feel — such  hypotheses  would  shock 
common  sense ;  because  we  all  know  that,  if  the  parts 
of  a  body  adhere  strongly,  it  is  hard,  although  it  should 
neither  emit  effluvia  nor  vibrate.  Yet,  at  the  same  time, 
no  man  can  say,  but  that  effluvia  or  the  vibration  of  the 
parts  of  a  body,  might  have  affected  our  touch,  in  the 
same  manner  that  hardness  now  does,  if  it  had  so  pleased 
the  Author  of  our  nature  ;  and,  if  either  of  these  hypoth- 
eses is  applied  to  explain  a  secondary  quality — such  as 
smell,  or  taste,  or  sound,  or  colour,  or  heat — there  ap- 
pears no  manifest  absurdity  in  the  supposition. 

The  distinction  betwixt  primary  and  secondary  quali- 
ties hath  had  several  revolutions.  Democritus  and  Epi- 
curus, and  their  followers,  maintained  it.  Aristotle  and 
the  Peripatetics  abolished  it.  Des  Cartes,  Malebranche, 
and  Locke,  revived  it,  and  were  thought  to  have  put  it 
in  a  very  clear  light.  But  Bishop  Berkeley  again  discard- 
ed this  distinction,  by  such  proofs  as  must  be  con- 
vincing to  those  that  hold  the  received  doctrine  of  ideas.  * 
Yet,  after  all,  there  appears  to  be  a  real  foundation  for 
it  in  the  principles  of  our  nature. 

What  hath  been  said  of  hardness,  is  so  easily  appli- 
cable not  only  to  its  opposite,  softness,  but  likewise  to 
roughness  and  smoothness,  to  figure  and  motion,  that  we 
may  be  excused  from  making  the  application,  which 
would  only  be  a  repetition  of  what  hath  been  said.  All 
these,  by  means  of  certain  corresponding  sensations  of 
touch,  are  presented  to  the  mind  as  real  external  quali- 
ties ;  the  conception  and  the  belief  of  them  are  invariably 

*  On  this  distinction  of  Primary  and  Secondary  Qualities,  see 
"Essays  on  the  Intellectual  Powers,"  Essay  II.,  chap.  17,  and 
Note  D,  at  the  end  of  the  volume.— H. 


SEC.  V.]  THE  PHILOSOPHY  OF  REID.  141 

connected  with  the  corresponding  sensations,  by  an 
original  principle  of  human  nature.  Their  sensations 
have  no  name  in  any  language  ;  they  have  not  only  been 
overlooked  by  the  vulgar,  but  by  philosophers  ;  or,  if 
they  have  been  at  all  taken  notice  of,  they  have  been 
confounded  with  the  external  qualities  which  they  sug- 
gest. 

Section   V. 

OF   EXTENSION. 

It  is  further  to  be  observed,  that  hardness  and  softness, 
roughness  and  smoothness,  figure  and  motion,  do  all 
suppose  extension,  and  cannot  be  conceived  without  it ; 
yet,  I  think  it  must,  on  the  other  hand,  be  allowed  that, 
if  we  had  never  felt  any  thing  hard  or  soft,  rough  or 
smooth,  figured  or  moved,  we  should  never  have  had  a 
conception  of  extension  ;*  so  that,  as  there  is  good 
ground  to  believe  that  the  notion  of  extension  could  not 
be  prior  to  that  of  other  primary  qualities,  so  it  is  cer- 
tain that  it  could  not  be  posterior  to  the  notion  of  any 
of  them,  being  necessarily  implied  in  them  all.f 

Extension,  therefore,  seems  to  be  a  quality  suggested 
to  us,  by  the  very  same  sensations  which  suggest  the 
other  qualities  above  mentioned.  When  I  grasp  a  ball 
in  my  hand,  I  perceive  it  at  once  hard,  figured,  and  ex- 

*  According  to  Reid,  Extension  (Space)  is  a  notion  a  posteriori, 
the  result  of  experience.  According  to  Kant,  it  is  a  priori  y  experi- 
ence only  affording  the  occasions  required  by  the  mind  to  exert  the 
acts,  of  which  the  intuition  of  space  is  a  condition.  To  the  former 
it  is  thus  a  contingent :  to  the  latter,  a  necessary  mental  possession. — H. 

f  In  this  paragraph,  to  say  nothing  of  others  in  the  "  Inquiry," 
Reid  evidently  excludes  sight  as  a  sense,  through  which  the  notion 
of  extension  or  space,  enters  into  the  mind.  In  his  later  work,  the 
"  Essays  on  the  Intellectual  Powers,"  he,  however,  expressly  allows 
that  function  to  sight  and  touch,  and  to  those  senses  alone.  See 
Essay  II.,  chap.  19,  p.  262,  quarto  edition. — H. 


142  THE  PHILOSOPHY  OF  REID.  [Cn.  V. 

tended.  The  feeling  is  very  simple,  and  hath  not  the 
least  resemblance  to  any  quality  of  body.  Yet  it  sug- 
gests to  us  three  primary  qualities  perfectly  distinct  from 
one  another,  as  well  as  from  the  sensation  which  indi- 
cates them.  When  I  move  my  hand  along  the  table, 
the  feeling  is  so  simple  that  I  find  it  difficult  to  distin- 
guish it  into  things  of  different  natures  ;  yet,  it  immedi- 
ately suggests  hardness,  smoothness,  extension,  and  mo- 
tion— things  of  very  different  natures,  and  all  of  them  as 
distinctly  understood  as  the  feeling  which  suggests 
them. 

We  are  commonly  told  by  philosophers,  that  we  get 
the  idea  of  extension  by  feeling  along  the  extremities  of 
a  body,  as  if  there  was  no  manner  of  difficulty  in  the 
matter.  I  have  sought,  with  great  pains,  I  confess,  to 
find  out  how  this  idea  can  be  got  by  feeling  ;  but  I  have 
sought  in  vain.  Yet  it  is  one  of  the  clearest  and  most 
distinct  notions  we  have  ;  nor  is  there  anything  whatso- 
ever about  which  the  human  understanding  can  carry  on 
so  many  long  and  demonstrative  trains  of  reasoning. 

The  notion  of  extension  is  so  familiar  to  us  from  in- 
fancy, and  so  constantly  obtruded  by  everything  we  see 
and  feel,  that  we  are  apt  to  think  it  obvious  how  it  comes 
into  the  mind  ;  but  upon  a  narrower  examination  we 
shall  find  it  utterly  inexplicable.  It  is  true  we  have 
feelings  of  touch,  which  every  moment  present  extension 
to  the  mind  ;  but  how  they  come  to  do  so,  is  the  ques- 
tion ;  for  those  feelings  do  no  more  resemble  extension, 
than  they  resemble  justice  or  courage — nor  can  the  ex- 
istence of  extended  things  be  inferred  from  those  feelings 
by  any  rules  of  reasoning ;  so  that  the  feelings  we  have 
by  touch,  can  neither  explain  how  we  get  the  notion, 
nor  how  we  come  by  the  belief  of  extended  things. 

What  hath  imposed  upon  philosophers  in  this  matter 
is,  that  the  feelings  of  touch,  which  suggest  primary 
qualities,  have  no  names,  nor  are  they  ever  reflected 
upon.  They  pass  through  the  mind  instantaneously, 


SEC.  V.)  THE  PHILOSOPHY  OP  REID.  143 

and  serve  only  to  introduce  the  notion  and  belief  of  ex- 
ternal things,  which,  by  our  constitution,  are  connected 
with  them.  They  are  natural  signs,  and  the  mind  im- 
mediately passes  to  the  thing  signified,  without  making 
the  least  reflection  upon  the  sign,  or  observing  that  there 
was  any  such  thing.  Hence  it  hath  always  been  taken 
for  granted,  that  the  ideas  of  extension,  figure,  and  mo- 
tion, are  ideas  of  sensation,  which  enter  into  the  mind 
by  the  sense  of  touch,  in  the  same  manner  as  the  sensa- 
tions of  sound  and  smell  do  by  the  ear  and  nose.  The 
sensations  of  touch  are  so  connected,  by  our  constitution, 
with  the  notions  of  extension,  figure,  and  motion,  that 
philosophers  have  mistaken  the  one  for  the  other,  and 
never  have  been  able  to  discern  that  they  were  not  only 
distinct  things,  but  altogether  unlike.  However,  if  we 
will  reason  distinctly  upon  this  subject,  we  ought  to  give 
names  to  those  feelings  of  touch ;  we  must  accustom 
ourselves  to  attend  to  them,  and  to  reflect  upon  them, 
that  we  may  be  able  to  disjoin  them  from,  and  to  compare 
them  with,  the  qualities  signified  or  suggested  by  them. 

The  habit  of  doing  this  is  not  to  be  attained  without 
pains  and  practice  ;  and  till  a  man  hath  acquired  this 
habit,  it  will  be  impossible  for  him  to  think  distinctly, 
or  to  judge  right,  upon  this  subject. 

Let  a  man  press  his  hand  against  the  table — he  feels 
it  hard.  But  what  is  the  meaning  of  this  ? — The  mean- 
ing undoubtedly  is,  that  he  hath  a  certain  feeling  of 
touch,  from  whickhe  concludes,  without  any  reasoning, 
or  comparing  ideas,  that  there  is  something  external 
really  existing,  whose  parts  stick  so  firmly  together, 
that  they  cannot  be  displaced  without  considerable  force. 

There  is  here  a  feeling,  and  a  conclusion  drawn  from 
it,  or  some  way  suggested  by  it.  In  order  to  compare 
these,  we  must  view  them  separately,  and  then  consider 
by  what  tie  they  are  connected,  and  wherein  they  resem- 
ble one  another.  The  hardness  of  the  table  is  the  con- 
clusion, the  feeling  is  the  medium  by  which  we  are  led 


144  TttE  PHILOSOPHY  OF  REID.  [CH.  V, 

to  that  conclusion.  Let  a  man  attend  distinctly  to  this 
medium,  and  to  the  conclusion,  and  he  will  perceive 
them  to  be  as  unlike  as  any  two  things  in  nature.  The 
one  is  a  sensation  of  the  mind,  which  can  have  no  ex- 
istence but  in  a  sentient  being  ;  nor  can  it  exist  one 
moment  longer  than  it  is  felt ;  the  other  is  in  the  table, 
and  we  conclude,  without  any  difficulty,  that  it  was  in 
the  table  before  it  was  felt,  and  continues  after  the  feel- 
ing is  over.  The  one  implies  no  kind  of  extension,  nor 
parts,  nor  cohesion  ;  the  other  implies  all  these.  Both, 
indeed,  admit  of  degrees,  and  the  feeling,  beyond  a  cer- 
tain degree,  is  a  species  of  pain  ;  but  adamantine  hard- 
ness does  not  imply  the  least  pain. 

And  as  the  feeling  hath  no  similitude  to  hardness,  so 
neither  can  our  reason  perceive  the  least  tie  or  connec- 
tion between  them  ;  nor  will  the  logician  ever  be  able  to 
shew  a  reason  why  we  should  conclude  hardness  from 
this  feeling,  rather  than  softness,  or  any  other  quality 
whatsoever.  But,  in  reality,  all  mankind  are  led  by 
their  constitution  to  conclude  hardness  from  this  feeling. 

The  sensation  of  heat,  and  the  sensation  we  have  by 
pressing  a  hard  body,  are  equally  feelings  ;  nor  can  we, 
by  reasoning,  draw  any  conclusion  from  the  one  but 
what  may  be  drawn  from  the  other  ;  but,  by  our  consti- 
tution, we  conclude  from  the  first  an  obscure  or  occult 
quality,  of  which  we  have  only  this  relative  conception, 
that  it  is  something  adapted  to  raise  in  us  the  sensation 
of  heat ;  from  the  second,  we  conclude  a  quality  of 
which  we  have  a  clear  and  distinct  conception — to  wit, 
the  hardness  of  the  body. 

Section    VI. 

OF    EXTENSION. 

To  put  this  matter  in  another  light,  it  may  be  proper 
to  try,  whether  from  sensation  alone  we  can  collect  any 


SEC.  VI.]  THE  PHILOSOPHY   OF   REID.  145 

notion  of  extension,  figure,  motion,  and  space.  I  take 
it  for  granted,  that  a  blind  man  hath  the  same  notions 
of  extension,  figure,  and  motion,  as  a  man  that  sees ; 
that  Dr.  Saunderson  had  the  same  notion  of  a  cone,  a 
cylinder,  and  a  sphere,  and  of  the  motions  and  distances 
of  the  heavenly  bodies,  as  Sir  Isaac  Newton. 

As  sight,  therefore,  is  not  necessary  for  our  acquiring 
those  notions,  we  shall  leave  it  out  altogether  in  our 
inquiry  into  the  first  origin  of  them  ;  and  shall  suppose 
a  blind  man,  by  some  strange  distemper,  to  have  lost  all 
the  experience,  and  habits,  and  notions  he  had  got  by 
touch  ;  not  to  have  the  least  conception  .of  the  existence, 
figure,  dimensions,  or  extension,  either  of  his  own  body, 
or  of  any  other ;  but  to  have  all  his  knowledge  of  exter- 
nal things  to  acquire  anew,  by  means  of  sensation,  and 
the  power  of  reason,  which  we  suppose  to  remain  entire. 

We  shall,  first,  suppose  his  body  fixed  immovably  in 
one  place,  and  that  he  can  only  have  the  feelings  of 
touch,  by  the  application  of  other  bodies  to  it.  Suppose 
him  first  to  be  pricked  with  a  pin — this  will,  no  doubt, 
give  a  smart  sensation:  he  feels  pain  ;  but  what  can  he 
infer  from  it  ?  Nothing,  surely,  with  regard  to  the  ex- 
istence or  figure  of  a  pin.  He  can  infer  nothing  from 
this  species  of  pain,  which  he  may  not  as  well  infer  from 
the  gout  or  sciatica.  Common  sense  may  lead  him  to 
think  that  this  pain  has  a  cause ;  but  whether  this  cause 
is  body  or  spirit,  extended  or  unextended,  figured  or  not 
figured,  he  cannot  possibly,  from  any  principles  he  is 
supposed  to  have,  form  the  least  conjecture.  Having 
had  formerly  no  notion  of  body  or  of  extension,  the 
prick  of  a  pin  can  give  him  none. 

Suppose,  next,  a  body  not  pointed,  but  blunt,  is  ap- 
plied to  his  body  with  a  force  gradually  increased  until 
it  bruises  him.  What  has  he  got  by  this,  but  another 
sensation  or  train  of  sensations,  from  which  he  is  able  to 
conclude  as  little  as  from  the  former?  A  scirrhous 
tumour  in  any  inward  part  of  the  body,  by  pressing  upon 


146  THE  PHILOSOPHY  OF   REID.  [CH.  V. 

the  adjacent  parts,  may  give  the  same  kind  of  sensation 
as  the  pressure  of  an  external  body,  without  conveying 
any  notion  but  that  of  pain,  which,  surely,  hath  no  re- 
semblance to  extension. 

Suppose,  thirdly,  that  the  body  applied  to  him  touches 
a  larger  or  a  lesser  part  of  his  body.  Can  this  give  him 
any  notion  of  its  extension  or  dimensions  ?  To  me  it 
seems  impossible  that  it  should,  unless  he  had  some 
previous  notion  of  the  dimensions  and  figure  of  his  own 
body,  to  serve  him  as  a  measure.  When  my  two  hands 
touch  the  extremities  of  a  body,  if  I  know  them  to  be  a 
foot  asunder,  I  easily  collect  that  the  body  is  a  foot 
long  ;  and,  if  I  know  them  to'  be  five  feet  asunder,  that 
it  is  five  feet  long  ;  but,  if  I  know  not  what  the  distance 
of  my  hands  is,  I  cannot  know  the  length  of  the  object 
they  grasp  ;  and,  if  I  have  no  previous  notion  of  hands 
at  all,  or  of  distance  between  them,  I  can  never  get  that 
notion  by  their  being  touched. 

Suppose,  again,  that  a  body  is  drawn  along  his  hands 
or  face,  while  they  are  at  rest.  Can  this  give  him  any 
notion  of  space  or  motion  ?  It  no  doubt  gives  a  new 
feeling ;  but  how  it  should  convey  a  notion  of  space  or 
motion  to  one  who  had  none  before,  I  cannot  conceive. 
The  blood  moves  along  the  arteries  and  veins,  and  this 
motion,  when  violent,  is  felt  :  but  I  imagine  no  man, 
by  this  feeling,  could  get  the  conception  of  space  or 
motion,  if  he  had  it  not  before.  Such  a  motion  may 
give  a  certain  succession  of  feelings,  as  the  colic  may  do  ; 
but  no  feelings,  nor  any  combination  of  feelings,  can 
ever  resemble  space  or  motion 

Let  us  next  suppose,  that  he  makes  some  instinctive 
effort  to  move  his  head  or  his  hand  ;  but  that  no  motion 
follows,  either  on  account  of  external  resistance,  or  of 
palsy.  Can  this  effort  convey  the  notion  of  space  and 
motion  to  one  who  never  had  it  before?  Surely  it 
cannot. 

Last  of  all,  let  us  suppose  that  he  moves  a  limb  by 


SEC.  VI.]  THE  PHILOSOPHY  OF  REID.  147 

instinct,  without  having  had  any  previous  notion  of  space 
or  motion.  He  has  here  a  new  sensation,  which  accom- 
panies the  flexure  of  joints,  and  the  swelling  of  muscles. 
But  how  this  sensation  can  convey  into  his  mind  the  idea 
of  space  and  motion,  is  still  altogether  mysterious  and 
unintelligible.  The  motions  of  the  heart  and  lungs  are 
all  performed  by  the  contraction  of  muscles,  yet  give  no 
conception  of  space  or  motion.  An  embryo  in  the  womb 
has  many  such  motions,  and  probably  the  feelings  that 
accompany  them,  without  any  idea  of  space  or  motion. 
Upon  the  whole,  it  appears  that  our  philosophers 
have  imposed  upon  themselves  and  upon  us,  in  pre- 
tending to  deduce  from  sensation  the  first  origin  of  our 
notions  of  external  existences,  of  space,  motion,  and  ex- 
tension,* and  all  the  primary  qualities  of  body — that  is, 
the  qualities  whereof  we  have  the  most  clear  and  distinct 
conception.  These  qualities  do  not  at  all  tally  with  any 
system  of  the  human  faculties  that  hath  been  advanced. 
They  have  no  resemblance  to  any  sensation,  or  to  any 
operation  of  our  minds  ;  and,  therefore,  they  cannot  be 
ideas  either  of  sensation  or  of  reflection.  The  very  con- 
ception of  them  is  irreconcilable  to  the  principles  of  all 
our  philosophic  systems  of  the  understanding.  The  be- 
lief of  them  is  no  less  so. 


*  That  the  notion  of  Space  is  a  necessary  condition  of  thought, 
and  that,  as  such,  it  is  inspossible  to  derive  it  from  experience,  has 
been  cogently  demonstrated  by  Kant.  But  that  we  may  not, 
through  sense,have  empirically  an  immediate  perception  of  some- 
thing extended,  I  have  yet  seen  no  valid  reason  to  doubt.  The 
a  priori  Conception  does  not  exclude  the  a  posteriori  Perception  ; 
and  this  latter  cannot  be  rejected  without  belying  the  evidence  of 
consciousness,  which  assures  us  that  we  are  immediately  cognizant, 
not  only  of  a  Setfb\it  of  a  Not  Se/f,  not  only  of  mind  but  of  matter: 
and  matter  cannot  be  immediately  known — that  is  known  as  existing 
— except  as  something  extended.  In  this,  however,  I  venture  a 
step  beyond  Reid  and  Stewart,  no  less  than  beyond  Kant;  though  I  am 
convinced  that  the  philosophy  of  the  two  former  tended  to  this  con- 
clusion, which  is,  in  fact,  that  of  the  common  sense  of  mankind, — H, 


148  THE  PHILOSOPHY  OF  REID.  [Cn.  V. 

Section  VII. 

OF  THE  EXISTENCE  OF  A  MATERIAL  WORLD. 

It  is  beyond  our  power  to  say  when,  or  in  what  order, 
we  came  by  our  notions  of  these  qualities.  When  we 
trace  the  operations  of  our  minds  as  far  back  as  memory 
and  reflection  can  carry  us,  we  find  them  already  in  pos- 
session of  our  imagination  and  belief,  and  quite  familiar 
to  the  mind  :  but  how  they  came  first  into  its  acquaint- 
ance, or  what  has  given  them  so  strong  a  hold  of  our  be- 
lief, and  what  regard  they  deserve,  are,  no  doubt,  very 
important  questions  in  the  philosophy  of  human  nature. 

Shall  we,  with  the  Bishop  of  Cloyne,  serve  them  with 
a  quo  warranto,  and  have  them  tried  at  the  bar  of  philos- 
ophy, upon  the  statute  of  the  ideal  system  ?  Indeed,  in 
this  trial  they  seem  to  have  come  off  very  pitifully  ;  for, 
although  they  had  very  able  counsel,  learned  in  the  law 
— viz.,  Des  Cartes,  Malebranche,  and  Locke,  who  said 
everything  they  could  for  their  clients — the  Bishop  of 
Cloyne,  believing  them  to  be  aiders  and  abetters  of 
heresy  and  schism,  prosecuted  them  with  great  vigour, 
fully  answered  all  that  had  been  pleaded  in  their  defence, 
and  silenced  their  ablest  advocates,  who  seem,  for  half  a 
century  past,  to  decline  the  argument,  and  to  trust  to 
the  favour  of  the  jury  rather  than  to  the  strength  of  their 
pleadings. 

Thus,  the  wisdom  of  philosophy  is  set  in  opposition  to 
the  common  sense  of  mankind.  The  first  pretends  to  de- 
monstrate, a  priori,  that  there  can  be  no  such  thing  as  a 
material  world;  that  sun,  moon,  stars,  and  earth,  vegeta- 
ble and  animal  bodies,  are,  and  can  be  nothing  else,  but 
sensations  in  the  mind,  or  images  of  those  sensations  in 
the  memory  and  imagination;  that,  like  pain  and  joy, 
they  can  have  no  existence  when  they  are  not  thought 
of.  The  last  can  conceive  no  otherwise  of  this  opinion, 
than  as  a  kind  of  metaphysical  lunacy,  and  concludes 


SEC.  VII.]  THE  PHILOSOPHY   OF  REID.  149 

that  too  much  learning  is  apt  to  make  men  mad;  and 
that  the  man  who  seriously  entertains  this  belief,  though 
in  other  respects  he  may  be  a  very  good  man,  as  a  man 
may  be  who  believes  that  he  is  made  of  glass;  yet,  surely 
he  hath  a  soft  place  in  his  understanding,  and  hath  been 
hurt  by  much  thinking. 

This  opposition  betwixt  philosophy  and  common 
sense,  is  apt  to  have  a  very  unhappy  influence  upon  the 
philosopher  himself.  He  sees  human  nature  in  an  odd, 
unamiable,  and  mortifying  light  He  considers  himself, 
and  the  rest  of  his  species,  as  born  under  a  necessity  of 
believing  ten  thousand  absurdities  and  contradictions, 
and  endowed  with  such  a  pittance  of  reason  as  is  just 
sufficient  to  make  this  unhappy  discovery:  and  this  is  all 
the  fruit  of  his  profound  speculations.  Such  notions  of 
human  nature  tend  to  slacken  every  nerve  of  the  soul,  to 
put  every  noble  purpose  and  sentiment  out  of  counte- 
nance, and  spread  a  melancholy  gloom  over  the  whole 
face  of  things. 

If  this  is  wisdom,  let  me  be  deluded  with  the  vulgar. 
I  find  something  within  me  that  recoils  against  it,  and 
inspires  more  reverent  sentiments  of  the  human  kind, 
and  of  the  universal  administration.  Common  Sense 
and  Reason  *  have  both  one  author;  that  Almighty  Au- 
thor in  all  whose  other  works  we  observe  a  consistency, 
uniformity,  and  beauty  which  charm  and  delight  the  un- 
derstanding: there  must,  therefore,  be  some  order  and 
consistency  in  the  human  faculties,  as  well  as  in  other 
parts  of  his  workmanship.  A  man  that  thinks  reverent- 
ly of  his  own  kind,  and  esteems  true  wisdom  and  philos- 
ophy, will  not  be  fond,  nay,  will  be  very  suspicious,  of 
such  strange  and  paradoxical  opinions.  If  they  are 
false,  they  disgrace  philosophy;  and,  if  they  are  true, 


*  The  reader  will  again  notice  this  and  the  other  instances  which 
follow,  of  the  inaccuracy  of  Reid's  language  in  his  earlier  work,  con- 
stituting, as  different,  Reason  and  Common  Sense. — H. 


150  THE   PHILOSOPHY    OF   REID.  [Cn.  V. 

they  degrade  the  human  species,  and  make  us  justly 
ashamed  of  our  frame. 

To  what  purpose  is  it  for  philosophy  to  decide  against 
common  sense  in  this  or  any  other  matter  ?  The  belief 
of  a  material  world  is  older,  and  of  more  authority,  than 
any  principles  of  philosophy.  It  declines  the  tribunal 
of  reason,*  and  laughs  at  all  the  artillery  of  the  logician. 
It  retains  its  sovereign  authority  in  spite  of  all  the  edicts 
of  philosophy,  and  reason  itself  must  stoop  to  its  orders. 
Even  those  philosophers  who  have  disowned  the  author- 
ity of  our  notions  of  an  external  material  world,  confess 
that  they  find  themselves  under  a  necessity  of  submitting 
to  their  power. 

Methinks,  therefore,  it  were  better  to  make  a  virtue  of 
necessity;  and,  since  we  cannot  get  rid  of  the  vulgar 
notion  and  belief  of  an  external  world,  to  reconcile  our 
reason  to  it  as  well  as  we  can;  for,  if  Reason*  should 
stomach  and  fret  ever  so  much  at  this  yoke,  she  cannot 
throw  it  off;  if  she  will  not  be  the  servant  of  Common 
Sense,  she  must  be  her  slave. 

In  order,  therefore,  to  reconcile  Reason  to  Common 
Sense*  in  this  matter,  I  beg  leave  to  offer  to  the  consid- 
eration of  philosophers  these  two  observations.  First, 
That,  in  all  this  debate  about  the  existence  of  a  material 
world,  it  hath  been  taken  for  granted  on  both  sides,  that 
this  same  material  world,  if  any  such  there  be,  must  be 
the  express  image  of  our  sensations  ;  that  we  can  have 
no  conception  of  any  material  thing  which  is  not  like 
some  sensation  in  our  minds;  and  particularly  that  the  sen- 
sations of  touch  are  images  of  extension,  hardness,  figure, 
and  motion.  Every  argument  brought  against  the  exist- 
ence of  a  material  world,  either  by  the  Bishop  of  Cloyne,  or 
by  the  author  of  the  "  Treatise  of  Human  Nature,"  sup- 
poseth  this.  If  this  is  true,  their  arguments  are  conclu- 
sive and  unanswerable;  but,  on  the  other  hand,  if  it  is 

*  See  last  note.— H. 


SEC.  VII.]  THE  PHILOSOPHY   OF  REID  151 

not  true,  there  is  no  shadow  of  argument  left.  Have 
those  philosophers,  then,  given  any  solid  proof  of  this 
hypothesis,  upon  which  the  whole  weight  of  so  strange 
a  system  rests.  No.  They  have  not  so  much  as  at- 
tempted to  do  it.  But,  because  ancient  and  modern 
philosophers  have  agreed  in  this  opinion,  they  have  taken 
it  for  granted.  But  let  us,  as  becomes  philosophers,  lay 
aside  authority;  we  need  not,  surely,  consult  Aristotle  or 
Locke,  to  know  whether  pain  be  like  the  point  of  a 
sword.  I  have  as  clear  a  conception  of  extension,  hard- 
ness, and  motion,  as  I  have  of  the  point  of  a  sword;  and, 
with  some  pains  and  practice,  I  can  form  as  clear  a  no- 
tion of  the  other  sensations  of  touch  as  I  have  of  pain. 
When  I  do  so,  and  compare  them  together,  it  appears  to 
me  clear  as  daylight,  that  the  former  are  not  of  kin  to 
the  latter,  nor  resemble  them  in  any  one  feature.  They 
are  as  unlike,  yea  as  certainly  and  manifestly  unlike,  as 
pain  is  to  the  point  of  a  sword.  It  may  be  true,  that 
those  sensations  first  introduced  the  material  world  to 
our  acquaintance;  it  may  be  true,  that  it  seldom  or  never 
appears  without  their  company;  but,  for  all  that,  they 
are  as  unlike  as  the  passion  of  anger  is  to  those  features 
of  the  countenance  which  attend  it. 

So  that,  in  the  sentence  those  philosophers  have  passed 
against  the  material  world,  there  is  an  error  persona. 
Their  proof  touches  not  matter,  or  any  of  its  qualities; 
but  strikes  directly  against  an  idol  of  their  own  imagina- 
tion, a  material  world  made  of  ideas  and  sensations, 
which  never  had  nor  can  have  an  existence. 

Secondly,  The  very  existence  of  our  conceptions  of 
extension,  figure  and  motion,  since  they  are  neither  ideas 
of  sensation  nor  reflection,  overturns  the  whole  ideal 
system,  by  which  the  material  world  hath  been  tried 
and  condemned;*  so  that  there  hath  been  likewise  in 
this  sentence  an  error  juris. 

*It  only  overturns  that  Idealism  founded  on  the  clumsy  hypothe- 
sis of  ideas  being  something  different,  both  from  the  reality  they 


152  THE  PHILOSOPHY   OF   REID,  [Cn.  V. 

It  is  a  very  fine  and  a  just  observation  of  Locke,  that,  as 
no  human  art  can  create  a  single  particle  of  matter,  and 
the  whole  extent  of  our  power  over  the  material  world 
consists  in  compounding,  combining,  and  disjoining 
the  matter  made  to  our  hands;  so,  in  the  world  of 
thought,  the  materials  are  all  made  by  nature,  and  can 
only  be  variously  combined  and  disjoined  by  us.  So 
that  it  is  impossible  for  reason  or  prejudice,  true  or  false 
philosophy,  to  produce  one  simple  notion  or  conception, 
which  is  not  the  work  of  nature,  and  the  result  of  our 
constitution.  The  conception  of  extension,  motion,  and 
the  other  attributes  of  matter,  cannot  be  the  effect  of 
error  or  prejudice;  it  must  be  the  work  of  nature.  And 
the  power  or  faculty  by  which  we  acquire  those  concep- 
tions, must  be  something  different  from  any  power  of  the 
human  mind  that  hath  been  explained,  since  it  is  neither 
sensation  nor  reflection. 

This  I  would,  therefore,  humbly  propose,  as  an  exper- 
imentum  cruets,  by  which  the  ideal  system  must  stand  or 
fall;  and  it  brings  the  matter  to  a  short  issue:  Extension, 
figure,  motion,  may,  any  one  or  all  of  them,  be  taken 
for  the  subject  of  this  experiment.  Either  they  are  ideas 
of  sensation,  or  they  are  not.  If  any  one  of  them  can 
be  shewn  to  be  an  idea  of  sensation,  or  to  have  the  least 
resemblance  to  any  sensation,  I  lay  my  hand  upon  my 
mouth,  and  give  up  all  pretense  to  reconcile  reason 
to  common  sense  in  this  matter,  and  must  suffer  the 
ideal  scepticism  to  triumph.  But  if,  on  the  other  hand, 
they  are  not  ideas  of  sensation,  nor  like  to  any  sen- 
sation, then  the  ideal  system  is  a  rope  of  sand,  and 
all  the  laboured  arguments  of  the  sceptical  philosophy 
against  a  material  world,  and  against  the  existence  of 


represent,  and  from  the  mind  contemplating  their  representation,  and 
which,  also,  derives  all  such  ideas  from  without.  This  doctrine 
may  subvert  the  Idealism  of  Berkeley,  but  it  even  supplies  a  basis 
for  an  Idealism  like  that  of  Fichte.— H. 


SEC.  VII.]  THE  PHILOSOPHY   OP  REID.  153 

everything  but  impressions  and  ideas,  proceed  upon  a 
false  hypothesis. 

If  our  philosophy  concerning  the  mind  be  so  lame 
with  regard  to  the  origin  of  our  notions  of  the  clearest, 
most  simple,  and  most  familiar  objects  of  thought,  and 
the  powers  from  which  they  are  derived,  can  we  expect 
that  it  should  be  more  perfect  in  the  account  it  gives  of 
the  origin  of  our  opinions  and  belief?  We  have  seen 
already  some  instances  of  its  imperfection  in  this  respect: 
and,  perhaps,  that  same  nature  which  hath  given  us  the 
power  to  conceive  things  altogether  unlike  to  any  of  our 
sensations,  or  to  any  operation  of  our  minds,  hath  like- 
wise provided  for  our  belief  of  them,  by  some  part  of  our 
constitution  hitherto  not  explained. 

Bishop  Berkeley  hath  proved,  beyond  the  possibility 
of  reply,  that  we  cannot  by  reasoning  infer  the  existence 
of  matter  from  our  sensations  ;  and  the  author  of  the 
"Treatise  of  Human  Nature"  hath  proved  no  less  clearly, 
that  we  cannot  by  reasoning  infer  the  existence  of  our 
own  or  other  minds  from  our  sensations.  But  are  we  to 
admit  nothing  but  what  can  be  proved  by  reasoning? 
Then  we  must  be  sceptics  indeed,  and  believe  nothing 
at  all.  The  author  of  the  "Treatise  of  Human  Nature" 
appears  to  me  to  be,  but  a  half-sceptic.  He  hath  not 
followed  his  principles  so  far  as  they  lead  him;  but,  after 
having,  with  unparalleled  intrepidity  and  success,  com- 
bated vulgar  prejudices,  when  he  had  but  one  blow  to 
strike,  his  courage  fails  him,  he  fairly  lays  down  his  arms, 
and  yields  himself  a  captive  to  the  most  common  of  all 
vulgar  prejudices — I  mean  the  belief  of  the  existence  of 
his  own  impressions  and  ideas. 

I  beg,  therefore,  to  have  the  honour  of  making  an  ad- 
dition to  the  sceptical  system,  without  which  I  conceive 
it  cannot  hang  together.  I  affirm,  that  the  belief  of  the 
existence  of  impressions  and  ideas,  is  as  little  supported 
by  reason,  as  that  of  the  existence  of  minds  and  bodies. 
No  man  ever  did  or  could  offer  any  reason  for  this  belief. 


1$4  THE  PHILOSOPHY  OF  REID.  [CH,  V. 

Des  Cartes  took  it  for  granted,  that  he  thought,  and  had 
sensations  and  ideas;  so  have  all  his  followers  done. 
Even  the  hero  of  scepticism  hath  yielded  this  point,  I 
crave  leave  to  say,  weakly  and  imprudently.  I  say  so, 
because  I  am  persuaded  that  there  is  no  principle  of  his 
philosophy  that  obliged  him  to  make  this  concession. 
And  what  is  there  in  impressions  and  ideas  so  formida- 
ble, that  this  all-conquering  philosophy,  after  triumph- 
ing over  every  other  existence,  should  pay  homage  to 
them?  Besides,  the  concession  is  dangerous:  for  belief 
is  of  such  a  nature,  that,  if  you  leave  any  root,  it  will 
spread;  and  you  may  more  easily  pull  it  up  altogether, 
than  say,  Hitherto  shalt  thou  go  and  no  further:  the  ex- 
istence of  impressions  and  ideas  I  give  up  to  thee;  but 
see  thou  pretend  to  nothing  more.  A  thorough  and  con- 
sistent sceptic  will  never,  therefore,  yield  this  point;  and 
while  he  holds  it,  you  can  never  oblige  him  to  yield  any- 
thing else. 

To  such  a  sceptic  I  have  nothing  to  say;  but  of  the 
semi-sceptics,  I  should  beg  to  know,  why  they  believe 
the  existence  of  their  impressions  and  ideas.  The  true 
reason  I  take  to  be,  because  they  cannot  help  it ;  and 
the  same  reason  will  lead  them  to  believe  many  other 
things. 

All  reasoning  must  be  from  first  principles  ;  and  for 
first  principles  no  other  reason  can  be  given  but  this, 
that,  by  the  constitution  of  our  nature,  we  are  under 
a  necessity  of  assenting  to  them.  Such  principles  are 
parts  of  our  constitution,  no  less  than  the  power  of  think- 
ing: reason  can  neither  make  nor  destroy  them;  nor  can 
it  do  anything  without  them:  it  is  like  a  telescope,  which 
may  help  a  man  to  see  farther,  who  hath  eyes;  but,  with- 
out eyes,  a  telescope  shews  nothing  at  all.  A  mathema- 
tician cannot  prove  the  truth  of  his  axioms,  nor  can  he 
prove  anything,  unless  he  takes  them  for  granted.  We 
cannot  prove  the  existence  of  our  minds,  nor  even  of  our 
thoughts  and  sensations.  A  historian,  or  a  witness,  can 


SEC.  VII.]  THE  PHILOSOPHY  OF  REID.  155 

prove  nothing,  unless  it  is  taken  for  granted  that  the 
memory  and  senses  may  be  trusted.  A  natural  philoso- 
pher can  prove  nothing,  unless  it  is  taken  for  granted 
that  the  course  of  nature  is  steady  and  uniform. 

How  or  when  I  got  such  first  principles,  upon  which  I 
build  all  my  reasoning,  I  know  not;  for  I  had  them  be- 
fore I  can  remember :  but  I  am  sure  they  are  parts  of 
my  constitution,  and  that  I  cannot  throw  them  off.  That 
our  thoughts  and  sensations  must  have  a  subject,  which 
we  call  ourself,  is  not  therefore  an  opinion  got  by  reason- 
ing, but  a  natural  principle.  That  our  sensations  of 
touch  indicate  something  external,  extended,  figured, 
hard  or  soft,  is  not  a  deduction  of  reason,  but  a  natural 
principle.  The  belief  of  it,  and  the  very  conception  of 
it,  are  equally  parts  of  our  constitution.  If  we  are  de- 
ceived in  it,  we  are  deceived  by  Him  that  made  us,  and 
there  is  no  remedy.  * 

I  do  not  mean  to  affirm,  that  the  sensations  of  touch 
do,  from  the  very  first,  suggest  the  same  notions  of  body 
and  its  qualities  which  they  do  when  we  are  grown  up. 
Perhaps  Nature  is  frugal  in  this,  as  in  her  other  opera- 
tions. The  passion  of  love,  with  all  its  concomitant 

*  The  philosophers  who  Have  most  loudly  appealed  to  the  veraci- 
ty of  God,  and  the  natural  conviction  of  mankind,  in  refutation  of 
certain  obnoxious  conclusions,  have  too  often  silently  contradicted 
that  yeracity  and  those  convictions,  when  opposed  to  certain  favour- 
ite opinions.  But  it  is  evident  that  such  authority  is  either  good  for 
all,  or  good  for  nothing.  Our  natural  consciousness  assures  us  (and 
\h&fact  of  that  assurance  is  admitted  by  philosophers  of  all  opin- 
ions) that  we  have  an  immediate  knowledge  of  the  very  things  them- 
selves of  an  external  and  extended  world;  and,  on  the  ground  of  this 
knowledge  alone,  is  the  belief  of  mankind  founded,  that  such  a 
world  really  exists.  Reid  ought,  therefore,  either  to  have  given  up 
his  doctrine  of  the  mere  suggestion  of  extension,  &c.,  as  subjective 
notions,  on  the  occasion  of  sensation,  or  not  to  appeal  to  the  Divine 
veracity,  and  the  common  sense  of  mankind,  in  favour  of  conclu- 
sions of  which  that  doctrine  subverts  the  foundation.  In  this  incon- 
sistency, Reid  has,  however,  besides  Des  Cartes,  many  distinguished 
copartners. — H. 


156  THE  PHILOSOPHY   OF  REID.  |CH.V. 

sentiments  and  desires,  is  naturally  suggested  by  the 
perception  of  beauty  in  the  other  sex;  yet  the  same  per- 
ception does  not  suggest  the  tender  passion  till  a  certain 
period  of  life.  A  blow  given  to  an  infant,  raises  grief 
and  lamentation;  but  when  he  grows  up,  it  as  naturally 
stirs  resentment,  and  prompts  him  to  resistance.  Per- 
haps a  child  in  the  womb,  or  for  some  short  period  of 
its  existence,  is  merely  a  sentient  being;  the  faculties  by 
which  it  perceives  an  external  world,  by  which  it  reflects 
on  its  own  thoughts,  and  existence,  and  relation  to  other 
things,  as  well  as  its  reasoning  and  moral  faculties,  un- 
fold themselves  by  degrees;  so  that  it  is  inspired  with  the 
various  principles  of  common  sense,  as  with  the  passions 
of  love  and  resentment,  when  it  has  occasion  for  them. 

Section    VIII. 

OF  THE  SYSTEMS  OF  PHILOSOPHERS  CONCERNING   THE    SENSES. 

All  the  systems  of  philosophers  about  our  senses  and 
their  objects  have  split  upon  this  rock,  of  not  distin- 
guishing properly  sensations  which  can  have  no  existence 
but  when  they  are  felt,  from  the  things  suggested  by 
them.  Aristotle — with  as  distinguishing  a  head  as  ever 
applied  to  philosophical  disquisitions — confounds  these 
two;  and  makes  every  sensation  to  be  the  form,  without 
the  matter,  of  the  thing  perceived  by  it.  As  the  impres- 
sion of  a  seal  upon  wax  has  the  form  of  the  seal  but 
nothing  of  the  matter  of  it,  so  he  conceived  our  sensa- 
tions to  be  impressions  upon  the  mind,  which  bear  the 
image,  likeness,  or  form  of  the  external  thing  perceived, 
without  the  matter  of  it.  Colour,  sound,  and  smell,  as 
well  as  extension,  figure,  and  hardness,  are,  according  to 
him,  various  forms  of  matter:  our  sensations  are  the  same 
forms  imprinted  on  the  mind,  and  perceived  in  its  own 
intellect.  It  is  evident  from  this,  that  Aristotle  made  no 
distinction  between  primary  and  secondary  qualities  of 


SEC.  VIII. ]  THE  PHILOSOPHY  OF  REID.  157 

bodies,  although  that  distinction  was  made  by  Democri- 
tus,  Epicurus,  and  others  of  the  ancients. 

Des  Cartes,  Malebranche,  and  Locke,  revived  the  dis- 
tinction between  primary  and  secondary  qualities  ;  but 
they  made  the  secondary  qualities  mere  sensations,  and 
the  primary  ones  resemblances  of  our  sensations.  They 
maintained  that  colour,  sound,  and  heat,  are  not  any- 
thing in  bodies,  but  sensations  of  the  mind  ;  at  the  same 
time,  they  acknowledged  some  particular  texture  or 
modification  of  the  body  to  be  the  cause  or  occasion  of 
those  sensations  ;  but  to  this  modification  they  gave  no 
name.  Whereas,  by  the  vulgar,  the  names  of  colour, 
heat,  and  sound,  are  but  rarely  applied  to  the  sensations, 
and  most  commonly  to  those  unknown  causes  of  them, 
as  hath  been  already  explained.  The  constitution  of  our 
nature  leads  us  rather  to  attend  to  the  things  signified  by 
the  sensation  than  to  the  sensation  itself,  and  to  give  a 
name  to  the  former  rather  than  to  the  latter.  Thus 
we  see,  that,  with  regard  to  secondary  qualities,  these 
philosophers  thought  with  the  vulgar,  and  with  common 
sense.  Their  paradoxes  were  only  an  abuse  of  words  ; 
for  when  they  maintain,  as  an  important  modern  dis- 
covery, that  there  is  no  Jieat  in  the  fire,  they  mean  no 
more,  than  that  the  fire  does  not  feel  heat,  which  every 
one  knew  before. 

With  regard  to  primary  qualities,  these  philosophers 
erred  more  grossly.  They  indeed  believed  the  existence 
of  those  qualities  ;  but  they  did  not  at  all  attend  to  the 
sensations  that  suggest  them,  which,  having  no  names, 
have  been  as  little  considered  as  if  they  had  no  existence. 
They  were  aware  that  figure,  extension,  and  hardness,  are 
perceived  by  means  of  sensations  of  touch  ;  whence  they 
rashly  concluded,  that  these  sensations  must  be  images 
and  resemblances  of  figure,  extension,  and  hardness. 

The  received  hypothesis  of  ideas  naturally  led  them  to 
this  conclusion:  and  indeed  cannot  consist  with  any 
other  ;  for,  according  to  that  hypothesis,  external  things 


*5&  THE  PHILOSOPHY  OF  REID.  [Cn.  V. 

must  be  perceived  by  means  of  images  of  them  in  the 
mind  ;  and  what  can  those  images  of  external  things  in 
the  mind  be,  but  the  sensations  by  which  we  perceive 
them  ? 

This,  however,  was  to  draw  a  conclusion  from  a  hy- 
pothesis against  fact.  We  need  not  have  recourse  to  any 
hypothesis  to  know  what  our  sensations  are,  or  what 
they  are  like.  By  a  proper  degree  of  reflection  and  at- 
tention we  may  understand  them  perfectly,  and  be  as 
certain  that  they  are  not  like  any  quality  of  body,  as  we 
can  be,  that  the  toothache  is  not  like  a  triangle.  How 
a  sensation  should  instantly  make  us  conceive  and  be- 
lieve the  existence  of  an  external  thing  altogether  un- 
like to  it,  I  do  not  pretend  to  know;  and  when  I  say  that 
the  one  suggests  the  other,  I  mean  not  to  explain  the 
manner  of  thek  connection,  but  to  express  a  fact,  which 
every  one  may  be  conscious  of — namely,  that,  by  a  law 
of  our  nature,  such  a  conception  and  belief  constantly 
and  immediately  follow  the  sensation. 

Bishop  Berkeley  gave  new  light  to  this  subject,  by 
shewing,  that  the  qualities  of  an  inanimate  thing,  such 
as  matter  is  conceived  to  be,  cannot  resemble  any  sen- 
sation; that  it  is  impossible  to  conceive  anything  like 
the  sensations  of  our  minds,  but  the  sensations  of  other 
minds.  Every  one  that  attends  properly  to  his  sensa- 
tions must  assent  to  this  :  yet  it  had  escaped  all  the  philos- 
ophers that  came  before  Berkeley;  it  had  escaped  even 
the  ingenious  Locke,  who  had  so  much  practised  reflec- 
tion on  the  operations  of  his  own  mind.  So  difficult  it 
is  to  attend  properly  even  to  our  own  feelings.  They 
are  so  accustomed  to  pass  through  the  mind  unobserved 
and  instantly  to  make  way  for  that  which  nature  intended 
them  to  signify,  that  it  is  extremely  difficult  to  stop,  and 
survey  them  ;  and  when  we  think  we  have  acquired  this 
power,  perhaps  the  mind  still  fluctuates  between  the 
sensation  and  its  associated  quality,  so  that  they  mix  to- 
gether, and  present  something  to  the  imagination  that  is 


SEC.  VIII.]  THE  PHILOSOPHY  OF  REID.  159 

compounded  of  both.  Thus,  in  a  globe  or  cylinder, 
whose  opposite  sides  are  quite  unlike  in  colour,  if  you 
turn  it  slowly,  the  colours  are  perfectly  distinguishable 
and  their  dissimilitude  is  manifest;  but  if  it  is  turned 
fast,  they  lose  their  distinction,  and  seem  to  be  of  one 
and  the  same  colour. 

No  succession  can  be  more  quick  than  that  of  tangi- 
ble qualities  to  the  sensations  with  which  nature  has  as- 
sociated them  ;  but  when  one  has  once  acquired  the  art 
of  making  them  separate  and  distinct  objects  of  thought, 
he  will  then  clearly  perceive  that  the  maxim  of  Bishop 
Berkeley, •  above-mentioned,  is  self-evident;  and  that  the 
features  of  the  face  are  not  more  unlike  to  a  passion  of 
the  mind  which  they  indicate,  than  the  sensations  of  touch 
are  to  the  primary  qualities  of  body. 

But  let  us  observe  what  use  the  Bishop  makes  of  this 
important  discovery.  Why,  he  concludes,  that  we  can 
have  no  conception  of  an  inanimate  substance,  such  as 
matter  is  conceived  to  be,  or  of  any  of  its  qualities  ; 
and  that  there  is  the  strongest  ground  to  believe  that 
there  is  no  existence  in  nature  but  minds,  sensations,  and 
ideas ;  if  there  is  any  other  kind  of  existence,  it  must  be 
what  we  neither  have  nor  can  have  any  conception  of. 
But  how  does  this  folloV?  Why,  thus:  We  can  have 
no  conception  of  anything  but  what  resembles  some  sen- 
sation or  idea  in  our  minds  ;  but  the  sensations  and  ideas 
in  our  minds  can  resemble  nothing  but  the  sensations 
and  ideas  in  other  minds ;  therefore,  the  conclusion  is 
evident.  This  argument,  we  see,  leans  upon  two  propo- 
sitions. The  last  of  them  the  ingenious  author  hath, 
indeed,  made  evident  to  all  that  understand  his  reason- 
ing, and  can  attend  to  their  own  sensations:  but  the  first 
proposition  he  never  attempts  to  prove ;  it  is  taken  from 
the  doctrine  of  ideas,  which  hath  been  so  universally  re- 
ceived by  philosophers,  that  it  was  thought  to  need  no 
proof. 

We  may  here  again  observe,  that  this  acute  writer  ar- 


160  THE  PHILOSOPHY  OF  REID.  [CH.  V. 

gues  from  a  hypothesis  against  fact,  and  against  the  com- 
mon sense  of  mankind.  That  we  can  have  no  concep- 
tion of  anything,  unless  there  is  some  impression,  sensa- 
tion, or  idea,  in  our  minds  which  resembles  it,  is  indeed 
an  opinion  which  hath  been  very  generally  received  among 
philosophers ;  but  it  is  neither  self-evident,  nor  hath  it 
been  clearly  proved  ;  and  therefore  it  hath  been  more 
reasonable  to  call  in  question  this  doctrine  of  philoso- 
phers, than  to  discard  the  material  world,  and  by  that 
means  expose  philosophy  to  the  ridicule  of  all  men  who 
will  not  offer  up  common  sense  as  a  sacrifice  to  meta- 
physics. 

We  ought,  however,  to  do  this  justice  both  to  the 
Bishop  of  Cloyne  and  to  the  author  of  the  "  Treatise  of 
Human  Nature,"  to  acknowledge,  that  their  conclusions 
are  justly  drawn  from  the  doctrine  of  ideas,  which  has 
been  so  universally  received.  On  the  other  hand,  from 
the  character  of  Bishop  Berkeley,  and  of  his  predecessors, 
Des  Cartes,  Locke,  and  Malebranche,  we  may  venture  to 
say,  that,  if  they  had  seen  all  the  consequences  of  this 
doctrine,  as  clearly  as  the  author  before  mentioned  did, 
they  would  -have  suspected  it  vehemently,  and  examined 
it  more  carefully  than  they  appear  to  have  done. 

The  theory  of  ideas,  like  the  Trojan  horse,  had  a 
specious  appearance  both  of  innocence  and  beauty ;  but 
if  those  philosophers  had  known  that  it  carried  in  its 
belly  death  and  destruction  to  all  science  and  common 
sense,  they  would  not  have  broken  down  their  walls  to 
give  it  admittance. 

That  we  have  clear  and  distinct  conceptions  of  exten- 
sion, figure,  motion,  and  other  attributes  of  body,  which 
are  neither  sensations,  nor  like  any  sensation,  is  a  fact  of 
which  we  may  be  as  certain  as  that  we  have  sensations. 
And  that  all  mankind  have  a  fixed  belief  of  an  external 
material  world — a  belief  which  is  neither  got  by  reason- 
ing nor  education,  and  a  belief  which  we  cannot  shake 
off,  even  when  we  seem  to  have  strong  arguments  against 


SEC.  VIII.]  THE  PHILOSOPHY  OF  REID.  l6l 

it  and  no  shadow  of  argument  for  it — is  likewise  a  fact, 
for  which  we  have  all  the  evidence  that  the  nature  of  the 
thing  admits.  These  facts  are  phaenomena  of  human 
nature,  from  which  we  may  justly  argue  against  any 
hypothesis,  however  generally  received.  But  to  argue 
from  a  hypothesis  against  facts,  is  contrary  to  the  rules 
of  true  philosophy. 


162  THE  PHILOSOPHY   OF  REID.  [C.H.  VI. 

CHAPTER  VI. 

OF  SEEING. 

Section  I. 

THE    EXCELLENCE    AND     DIGNITY   OF   THIS    FACULTY. 

THE  advances  made  in  the  knowledge  of  optics  in  the 
last  age  and  in  the  present,  and  chiefly  the  discoveries  of 
Sir  Isaac  Newton,  do  honour,  not  to  philosophy  only, 
but  to  human  nature.  Such  discoveries  ought  for  ever  to 
put  to  shame  the  ignoble  attempts  of  our  modern  sceptics 
to  depreciate  the  human  understanding,  and  to  dispirit 
men  in  the  search  of  truth,  by  representing  the  human 
faculties  as  fit  for  nothing  but  to  lead  us  into  absurdities 
and  contradictions. 

Of  the  faculties  called  the  five  senses,  sight  is  without 
doubt  the  noblest.  The  rays  of  light,  which  minister  to 
this  sense,  and  of  which,  without  it,  we  could  never  have 
had  the  least  conception,  are  the  most  wonderful  and 
astonishing  part  of  the  inanimate  creation.  We  must  be 
satisfied  of  this,  if  we  consider  their  extreme  minuteness; 
their  inconceivable  velocity;  the  regular  variety  of  colours 
which  they  exhibit;  the  invariable  laws  according  to  which 
they  are  acted  upon  by  other  bodies,  in  their  reflections, 
inflections,  and  refractions,  without  the  least  change  of 
their  original  properties  ;  and  the  facility  with  which 
they  pervade  bodies  of  great  density  and  of  the  closest 
texture,  without  resistance,  without  crowding  or  disturb- 
ing one  another,  without  giving  the  least  sensible  impulse 
to  the  lightest  bodies. 

The  structure  of  the  eye,  and  of  all  its  appurtenances, 
the  admirable  contrivances  of  nature  for  performing  all 


SEC.  I.]  THE  PHILOSOPHY   OF  REID.  163 

its  various  external  and  internal  motions,  and  the  variety 
in  the  eyes  of  different  animals,  suited  to  their  several 
natures  and  ways  of  life,  clearly  demonstrate  this  organ 
to  be  a  masterpiece  of  Nature's  work.  And  he  must  be 
very  ignorant  of  what  hath  been  discovered  about  it,  or 
have  a  very  strange  cast  of  understanding,  who  can  seri- 
ously doubt  whether  or  not  the  rays  of  light  and  the  eye 
were  made  for  one  another,  with  consummate  wisdom, 
and  perfect  skill  in  optics. 

If  we  shall  suppose  an  order  of  beings,  endued  with 
every  human  faculty  but  that  of  sight,  how  incredible 
would  it  appear  to  such  beings,  accustomed  only  to  the 
slow  informations  of  touch,  that,  by  the  addition  of  an 
organ  consisting  of  a  ball  and  socket  of  an  inch  diam- 
eter, they  might  be  enabled,  in  an  instant  of  time, 
without  changing  their  place  to  perceive  the  dis- 
position of  a  whole  army  or  the  order  of  a  battle,  the 
figure  of  a  magnificent  palace  or  all  the  variety  of  a 
landscape  !  If  a  man  were  by  feeling  to  find  out  the  fig- 
ure of  the  peak  of  Teneriffe,  or  even  of  St.  Peter's  Church 
at  Rome,  it  would  be  the  work  of  a  lifetime. 

It  would  appear  still  more  incredible  to  such  beings 
as  we  have  supposed,  if  they  were  informed  of  the  dis- 
coveries, which  may  be  made  by  this  little  organ  in 
things  far  beyond  the  reach  of  any  other  sense  :  that  by 
means  of  it  we  can  find  our  way  in  the  pathless  ocean  ; 
that  we  can  traverse  the  globe  of  the  earth,  determine 
its  figure  and  dimensions,  and  delineate  every  region  of 
it; — yea,  that  we  can  measure  the  planetary  orbs,  and 
make  discoveries  in  the  sphere  of  the  fixed  stars. 

Would  it  not  appear  still  more  astonishing  to  such 
beings,  if  they  should  be  farther  informed,  that,  by  means 
of  this  same  organ,  we  can  perceive  the  tempers  and  dis- 
positions, the  passions  and  affections,  of  our  fellow- 
creatures,  even  when  they  want  most  to  conceal  them  ? 
that,  when  the  tongue  is  taught  most  artfully  to  lie  and 
dissemble,  the  hypocrisy  should  appear  in  the  counte- 


164  THE  PHILOSOPHY  OF  REID.  [Cn.  VI. 

* 

nance  to  a  discerning  eye  ? — and  that,  by  this  organ,  we 
can  often  perceive  what  is  straight  and  what  is  crooked 
in  the  mind  as  well  as  in  the  body  ?  How  many  myste- 
rious things  must  a  blind  man  believe,  if  he  will  give 
credit  to  the  relations  of  those  that  see  ?  Surely  he 
needs  as  strong  a  faith  as  is  required  of  a  good  Christian. 
It  is  not  therefore  without  reason  that  the  faculty  of 
seeing  is  looked  upon,  not  only  as  more  noble  than 
the  other  senses,  but  as  having  something  in  it  of  a  na- 
ture superior  to  sensation.  The  evidence  of  reason  is 
called  seeing,  not  feeling,  smelling,  or  tasting.  Yea,  we 
are  wont  to  express  the  manner  of  the  Divine  knowledge 
by  seeing,  as  that  kind  of  knowledge  which  is  most  per- 
fect in  us. 

Section  IL 

SIGHT  DISCOVERS  ALMOST  NOTHING  WHICH  THE  BLIND    MAY 
NOT  COMPREHEND THE  REASON  OF  THIS. 

Notwithstanding  what  hath  been  said  of  the  dignity 
and  superior  nature  of  this  faculty,  it  is  worthy  of  our 
observation,  that  there  is  very  little  of  the  knowledge 
acquired  by  sight,  that  may  not  be  communicated  to  a 
man  born  blind.  One  who  never  saw  the  light,  may  be 
learned  and  knowing  in  every  science,  even  in  optics  ; 
and  may  make  discoveries  in  every  branch  of  philosophy. 
He  may  understand  as  much  as  another  man,  not  only 
of  the  order,  distances,  and  motions  of  the  heavenly 
bodies  ;  but  of  the  nature  of  light,  and  of  the  laws  of 
the  reflection  and  refraction  of  its  rays.  He  may  un- 
derstand distinctly  how  those  laws  produce  the  phaenom- 
ena  of  the  rainbow,  the  prism,  the  camera  obscura, 
and  the  magic  lanthorn,  and  all  the  powers  of  the  micro- 
scope and  telescope.  This  is  a  fact  sufficiently  attested 
by  experience. 

In  order  to  perceive  the  reason  of  it,  we  must  distin- 
guish the  appearance  that  objects  make  to  the  eye,  from 


SEC.  11.1  THE  PHILOSOPHY   OF   REID.  l6$ 

the  things  suggested  by  that  appearance ;  and  again,  in 
the  visible  appearance  of  objects,  we  must  distinguish 
the  appearance  of  colour  from  the  appearance  of  exten- 
sion, figure,  and  motion.  First,  then,  as  to  the  visible 
appearance  of  the  figure,  and  motion,  and  extension  of 
bodies,  I  conceive  that  a  man  born  blind  may  have  a 
distinct  notion,  if  not  of  the  very  things,  at  least  of  some- 
thing extremely  like  to  them.  May  not  a  blind  man  be 
made  to  conceive  that  a  body  moving  directly  from  the 
eye,  or  directly  towards  it,  may  appear  to  be  at  rest  ?  and 
that  the  same  motion  may  appear  quicker  or  slower,  ac- 
cording as  it  is  nearer  to  the  eye  or  farther  off,  more 
direct  or  more  oblique  ?  May  he  not  be  made  to  con- 
ceive, that  a  plain  surface,  in  a  certain  position,  may  ap- 
pear as  a  straight  line,  and  vary  its  visible  figure,  as  its 
position,  or  the  position  of  the  eye,  is  varied? — that 
a  circle  seen  obliquely  will  appear  an  ellipse  ;  and  a 
square,  a  rhombus,  or  an  oblong  rectangle  ?  Dr.  Saun- 
derson  understood  the  projection  of  the  sphere,  and  the 
common  rules  of  perspective  ;  and  if  he  did,  he  must 
have  understood  all  that  I  have  mentioned.  If  there 
were  any  doubt  of  Dr.  Saunderson's  understanding  these 
things,  I  could  mention  my  having  heard  him  say  in 
conversation,  that  he  found  great  difficulty  in  under- 
standing Dr.  Halley's  demonstration  of  that  proposition, 
that  the  angles  made  by  the  circles  of  the  sphere,  are 
equal  to  the  angles  made  by  their  representatives  in  the 
stereographic  projection  ;  but,  said  he,  when  I  laid  aside 
that  demonstration,  and  considered  the  proposition  in 
my  own  way,  I  saw  clearly  that  it  must  be  true.  Another 
gentleman,  of  undoubted  credit  and  judgment  in  these 
matters,  who  had  part  in  this  conversation,  remembers 
it  distinctly. 

As  to  the  appearance  of  colour,  a  blind  man  must  be 
more  at  a  loss  ;  because  he  hath  no  perception  that  resem- 
bles it.  Yet  he  may,  by  a  kind  of  analogy,  in  part  supply 
this  defect.  To  those  who  see,  a  scarlet  colour  signifies 


r66  THE  PHILOSOPHY   OF  REID.  [Cn.  VI. 

an  unknown  quality  in  bodies,  that  makes  to  the  eye  an 
appearance  which  they  are  well  acquainted  with  and 
have  often  observed — to  a  blind  man,  it  signifies  an  un- 
known quality,  that  makes  to  the  eye  an  appearance 
which  he  is  unacquainted  with.  But  he  can  conceive 
the  eye  to  be  variously  affected  by  different  colours,  as 
the  nose  is  by  different  smells,  or  the  ear  by  different 
sounds.  Thus  he  can.  conceive  scarlet  to  differ  from 
blue,  as  the  sound  of  a  trumpet  does  from  that  of  a  drum; 
or  as  the  smell  of  an  orange  differs  from  that  of  an  ap- 
ple. It  is  impossible  to  know  whether  a  scarlet  colour 
has  the  same  appearance  to  me  which  it  hath  to  another 
man  ;  and,  if  the  appearance  of  it  to  different  persons 
differed  as  much  as  colour  does  from  sound,  they  might 
never  be  able  to  discover  this  difference.  Hence  it  ap- 
pears obvious,  that  a  blind  man  might  talk  long  about 
colours  distinctly  and  pertinently ;  and,  if  you  were  to 
examine  him  in  the  dark  about  the  nature,  composition, 
and  beauty  of  them,  he  might  be  able  to  answer,  so  as 
not  to  betray  his  defect. 

We  have  seen  how  far  a  blind  man  may  go  in  the 
knowledge  of  the  appearances  which  things  make  to  the 
eye.  As  to  the  things  which  are  suggested  by  them  or 
inferred  from  them,  although  he  could  never  discover  them 
of  himself,  yet  he  may  understand  them  perfectly  by  the 
information  of  others.  And  everything  of  this  kind  that 
enters  into  our  minds  by  the  eye,  may  enter  into  his  by 
the  ear.  Thus,  for  instance,  he  could  never,  if  left  to 
the  direction  of  his  own  faculties,  have  dreamed  of  any 
such  thing  as  light ;  but  he  can  be  informed  of  every- 
thing we  know  about  it.  He  can  conceive,  as  distinctly 
as  we,  the  minuteness  and  velocity  of  its  rays,  their  vari- 
ous degrees  of  refrangibility  and  reflexibility,  and  all  the 
magical  powers  and  virtues  of  that  wonderful  element. 
He  could  never  of  himself  have  found  out,  that  there  are 
such  bodies  as  the  sun,  moon,  and  stars  ;  but  he  may  be 
informed  of  all  the  noble  discoveries  of  astronomers, 


SEC.  II.]  THE  PHILOSOPHY   OF   REID.  167 

about  their  motions,  and  the  laws  of  nature  by  which 
they  are  regulated.  Thus,  it  appears,  that  there  is  very 
little  knowledge  got  by  the  eye,  which  may  not  be  com- 
municated by  language  to  those  who  have  no  eyes. 

If  we  should  suppose  that  it  were  as  uncommon  for 
men  to  see  as  it  is  to  be  born  blind,  would  not  the  few 
who  had  this  rare  gift  appear  as  prophets  and  inspired 
teachers  to  the  many  ?  We  conceive  inspiration  to  give 
a  man  no  new  faculty,  but  to  communicate  to  him,  in  a 
new  way,  and  by  extraordinary  means,  what  the  facul- 
ties common  to  mankind  can  apprehend,  and  what  he 
can  communicate  to  others  by  ordinary  means.  On  the 
supposition  we  have  made,  sight  would  appear  to  the 
blind  very  similar  to  this  ;  for  the  few  who  had  this  gift, 
could  communicate  the  knowledge  acquired  by  it  tc 
those  who  had  it  not.  They  could  not,  indeed,  convey 
to  the  blind  any  distinct  notion  of  the  manner  in  which 
they  acquired  this  knowledge.  A  ball  and  socket  would 
seem,  to  a  blind  man,  in  this  case,  as  improper  an  instru- 
ment for  acquiring  such  a  variety  and  extent  of  know- 
ledge, as  a  dream  or  a  vision.  The  manner  in  which  a 
man  who  sees,  discerns  so  many  things  by  means  of  the 
eye,  is  as  unintelligible  to  the  blind,  as  the  manner  in 
which  a  man  may  be  inspired  with  knowledge  by  the 
Almighty,  is  to  us.  Ought  the  blind  man,  therefore, 
without  examination,  to  treat  all  pretences  to  the  gift  of 
seeing  as  imposture  ?  Might  he  not,  if  he  were  candid 
and  tractable,  find  reasonable  evidence  of  the  reality  of 
this  gift  in  others,  and  draw  great  advantages  from  it  to 
himself? 

The  distinction  we  have  made  between  the  visible  ap- 
pearances of  the  objects  of  sight,  and  things  suggested 
by  them,  is  necessary  to  give  us  a  just  notion  of  the  in- 
tention of  nature  in  giving  us  eyes.  If  we  attend  duly 
to  the  operation  of  our  mind  in  the  use  of  this  faculty, 
we  shall  perceive  that  the  visible  appearance  of  objects  is 
hardly  ever  regarded  by  us.  It  is  not  at  all  made  an 


168    '  THE  PHILOSOPHY   OF  REID.  [Cn.  VI. 

object  of  thought  or  reflection,  but  serves  only  as  a  sign 
to  introduce  to  the  mind  something  else,  which  may  be 
distinctly  conceived  by  those  who  never  saw. 

Thus,  the  visible  appearance  of  things  in  my  room 
varies  almost  every  hour,  according  as  the  day  is  clear 
or  cloudy,  as  the  sun  is  in  the  east,  or  south,  or  west, 
and  as  my  eye  is  in  one  part  of  the  room  or  in  another  ; 
but  I  never  think  of  these  variations,  otherwise  than  as 
signs  of  morning,  noon,  or  night,  of  a  clear  or  cloudy 
sky.  A  book  or  a  chair  has  a  different  appearance  to 
the  eye,  in  every  different  distance  and  position  ;  yet  we 
conceive  it  to  be  still  the  same;  and,  overlooking  the 
appearance,  we  immediately  conceive  the  real  figure,  dis- 
tance, and  position  of  the  body,  of  which  its  visible  or 
perspective  appearance  is  a  sign  and  indication. 

When  I  see  a  man  at  the  distance  of  ten  yards,  and 
afterwards  see  him  at  the  distance  of  a  hundred  yards, 
his  visible  appearance,  in  its  length,  breadth,  and  all  its 
linear  proportions,  is  ten  times  less  in  the  last  case  than 
it  is  in  the  first ;  yet  I  do  not  conceive  him  one  inch  di- 
minished by  this  diminution  of  his  visible  figure.  Nay, 
I  do  not  in  the  least  attend  to  this  diminution,  even  when 
I  draw  from  it  the  conclusion  of  his  being  at  a  greater 
distance.  For  such  is  the  subtilty  of  the  mind's  opera- 
tion in  this  case,  that  we  draw  the  conclusion,  without 
perceiving  that  ever  the  premises  entered  into  the  mind. 
A  thousand  such  instances  might  be  produced,  in  order 
to  shew  that  the  visible  appearances  of  objects  are  in- 
tended by  nature  only  as  signs  or  indications  ;  and  that 
the  mind  passes  instantly  to  the  things  signified,  without 
making  the  least  reflection  upon  the  sign,  or  even  per- 
ceiving that  there  is  any  such  thing.  It  is  in  a  way  some- 
what similar,  that  the  sounds  of  a  language,  after  it  is  be- 
come familiar,  are  overlooked,  and  we  attend  only  to 
the  things  signified  by  them. 

It  is  therefore  a  just  and  important  observation  of  the 
Bishop  of  Cloyne,  That  the  visible  appearance  of  objects 


SEC.  III.]  THE  PHILOSOPHY  Of  RElD.  169 

is  a  kind  of  language  used  by  nature,  to  inform  us  of 
their  distance,  magnitude,  and  figure.  And  this  obser- 
vation hath  been  very  happily  applied  by  that  ingenious 
writer,  to  the  solution  of  some  phaenomena  in  optics, 
which  had  before  perplexed  the  greatest  masters  in  that 
science.  The  same  observation  is  further  improved  by 
the  judicious  Dr.  Smith,  in  his  Optics,  for  explaining  the 
apparent  figure  of  the  heavens,  and  the  apparent  distances 
and  magnitudes  of  objects  seen  with  glasses,  or  by  the 
naked  eye. 

Avoiding  as  much  as  possible  the  repetition  of  what 
hath  been  said  by  these  excellent  writers,  we  shall  avail 
ourselves  of  the  distinction  between  the  signs  that  nature 
useth  in  this  visual  language,  and  the  things  signified  by 
them;  and  in  what  remains  to  be  said  of  sight,  shall  first 
make  some  observations  upon  the  signs. 

Section  HI. 

OF  THE  VISIBLE  APPEARANCES  OF  OBJECTS. 

In  this  section  we  must  speak  of  things  which  are 
never  made  the  object  of  reflection,  though  almost 
every  moment  presented  to  the  mind.  Nature  intended 
them  only  for  signs  ;  and  in  the  whole  course  of  life  they 
are  put  to  no  other  use.  The  mind  has  acquired  a  con- 
firmed and  inveterate  habit  of  inattention  to  them  ;  for 
they  no  sooner  appear,  than  quick  as  lightning  the  thing 
signified  succeeds,  and  engrosses  all  our  regard.  They 
have  no  name  in  language ;  and,  although  we  are  con- 
scious of  them  when  they  pass  through  the  mind,  yet 
their  passage  is  so  quick  and  so  familiar,  that  it  is  abso- 
lutely unheeded ;  nor  do  they  leave  any  footsteps  of  them- 
selves, either  in  the  memory  or  imagination.  That  this 
is  the  case  with  regard  to  the  sensations  of  touch,  hath 
been  shewn  in  the  last  chapter ;  and  it  holds  no  less  with 
regard  to  the  visible  appearances  of  objects. 


170  THE  PHILOSOPHY  OF   REID.  tCn.  VI. 

I  cannot  therefore  entertain  the  hope  of  being  intelligi- 
ble to  those  readers  who  have  not,  by  pains  and  prac- 
tice, acquired  the  habit  of  distinguishing  the  appearance 
of  objects  to  the  eye,  from  the  judgment  which  we  form 
by  sight  of  their  colour,  distance,  magnitude,  and  figure. 

The  only  profession  in  life  wherein  it  is  necessary  to 
make  this  distinction,  is  that  of  painting.  The  painter 
hath  occasion  for  an  abstraction,  with  regard  to  visible 
objects,  somewhat  similar  to  that  which  we  here  require  : 
and  this  indeed  is  the  most  difficult  part  of  his  art.  For 
it  is  evident,  that,  if  he  could  fix  in  his  imagination  the 
visible  appearance  of  objects,  without  confounding  it  with 
the  things  signified  by  that  appearance,  it  would  be  as 
easy  for  him  to  paint  from  the  life,  and  to  give  every 
figure  its  proper  shading  and  relief,  and  its  perspective 
proportions,  as  it  is  to  paint  from  a  copy.  Perspective, 
shading,  giving  relief,  and  colouring,  are  nothing  else 
but  copying  the  appearance  which  things  make  to  the 
eye.  We  may  therefore  borrow  some  light  on  the  subject 
of  visible  appearance  from  this  art. 

Let  one  look  upon  any  familiar  object,  such  as  a  book, 
at  different  distances  and  in  different  positions  :  is  he  not 
able  to  affirm,  upon  the  testimony  of  his  sight,  that  it  is 
the  same  book,  the  same  object,  whether  seen  at  the  dis- 
tance of  one  foot  or  of  ten,  whether  in  one  position  or 
another ;  that  the  colour  is  the  same,  the  dimensions  the 
same,  and  the  figure  the  same,  as  far  as  the  eye  can 
judge  ?  This  surely  must  be  acknowledged.  The  same 
individual  object  is  presented  to  the  mind,  only  placed 
at  different  distances  and  in  different  positions.  Let  me 
ask,  in  the  next  place,  Whether  this  object  has  the  same 
appearance  to  the  eye  in  these  different  distances  ?  In- 
fallibly it  hath  not.  For, 

First,  However  certain  our  judgment  may  be  that  the 
colour  is  the  same,  it  is  as  certain  that  it  hath  not  the 
same  appearance  at  different  distances.  There  is  a  cer- 
tain degradation  of  the  colour,  and  a  certain  confusion 


SEC.  III.]  THE  PHILOSOPHY  OF  REID.  171 

and  indistinctness  of  the  minute  parts,  which  is  the  natu- 
ral consequence  of  the  removal  of  the  object  to  a  greater 
distance.  Those  that  are  not  painters,  or  critics  in 
painting,  overlook  this  ;  and  cannot  easily  be  persuaded, 
that  the  colour  of  the  same  object  hath  a  different  appear- 
ance at  the  distance  of  one  foot  and  of  ten,  in  the 
shade  and  in  the  light.  But  the  masters  in  painting 
know  how,  by  the  degradation  of  the-  colour  and  the 
confusion  of  the  minute  parts,  figures  which  are  upon 
the  same  canvas,  and  at  the  same  distance  from  the  eye, 
may  be  made  to  represent  objects  which  are  at  the  most 
unequal  distances.  They  know  how  to  make  the  ob- 
jects appear  to  be  of  the  same  colour,  by  making  their 
pictures  really  of  different  colours,  according  to  their 
distances  or  shades. 

Secondly,  Every  one  who  is  acquainted  with  the  rules 
of  perspective,  knows  that  the  appearance  of  the  figure 
of  the  book  must  vary  in  every  different  position:  yet  if 
you  ask  a  man  that  has  no  notion  of  perspective,  whether 
the  figure  of  it  does  not  appear  to  his  eye  to  be  the  same 
in  all  its  different  positions  ?  he  can  with  a  good  con- 
science affirm  that  it  does.  He  hath  learned  to  make 
allowance  for  the  variety  of  visible  figure  arising  from 
the  difference  of  position,  and  to  draw  the  proper  con- 
clusions from  it.  But  he  draws  these  conclusions  so 
readily  and  habitually,  as  to  lose  sight  of  the  premises  : 
and  therefore  where  he  hath  made  the  same  conclusion, 
he  conceives  the  visible  appearance  must  have  been  the 
same. 

Thirdly,  Let  us  consider  the  apparent  magnitude  or 
dimensions  of  the  book.  Whether  I  view  it  at  the  dis- 
tance of  one  foot  or  of  ten  feet,  it  seems  to  be  about  seven 
inches  long,  five  broad,  and  one  thick.  I  can  judge  of 
these  dimensions  very  nearly  by  the  eye,  and  I  judge 
them  to  be  the  same  at  both  distances.  But  yet  it  is 
certain,  that,  at  the  distance  of  one  foot,  its  visible  length 
and  breadth  is  about  ten  times  as  great  as  at  the  distance  of 


172  THE  PHILOSOPHY  OF  REID.  [Cn.  VI. 

ten  feet ;  and  consequently  its  surface  is  about  a  hun- 
dred times  as  great.  This  great  change  of  apparent 
magnitude  is  altogether  overlooked,  and  every  man  is 
apt  to  imagine,  that  it  appears  to  the  eye  of  the  same 
size  at  both  distances.  Further,  when  I  look  at  the  book, 
it  seems  plainly  to  have  three  dimensions,  of  length, 
breadth,  and  thickness :  but  it  is  certain  that  the  visible 
appearance  hath  no  more  than  two,  and  can  be  exactly 
represented  upon  a  canvas  which  hath  only  length  and 
breadth. 

In  the  last  place,  does  not  every  man,  by  sight,  per- 
ceive the  distance  of  the  book  from  his  eye  ?  Can  he 
not  affirm  with  certainty,  that  in  one  case  it  is  not  above 
one  foot  distant,  that  in  another  it  is  ten  ?  Nevertheless, 
it  appears  certain,  that  distance  from  the  eye  is  no  im- 
mediate object  of  sight.  There  are  certain  things  in 
the  visible  appearance,  which  are  signs  of  distance  from 
the  eye,  and  from  which,  as  we  shall  afterwards  shew,  we 
learn  by  experience  to  judge  of  that  distance  within  cer- 
tain limits  ;  but  it  seems  beyond  doubt,  that  a  man  born 
blind,  and  suddenly  made  to  see,  could  form  no  judg- 
ment at  first  of  the  distance  of  the  objects  which  he  saw. 

The  young  man  couched  by  Cheselden  thought,  at 
first,  that  everything  he  saw  touched  his  eye,  and  learned 
only  by  experience  to  judge  of  the  distance  of  visible 
objects. 

I  have  entered  into  this  long  detail,  in  order  to  shew 
that  the  visible  appearance  of  an  object  is  extremely 
different  from  the  notion  of  it  which  experience  teaches 
us  to  form  by  sight ;  and  to  enable  the  reader  to  attend 
to  the  visible  appearance  of  colour,  figure,  and  extension, 
in  visible  things,  which  is  no  common  object  of  thought, 
but  must  be  carefully  attended  to  by  those  who  would 
enter  into  the  philosophy  of  this  sense,  or  would  com- 
prehend what  shall  be  said  upon  it.  To  a  man  newly 
made  to  see,  the  visible  appearance  of  objects  would  be 
the  same  as  to  us  ;  but  he  would  see  nothing  at  all  of 


SEC.IV.]  THE  PHILOSOPHY   OF  REID.  173 

their  real  dimensions,  as  we  do.  He  could  form  no 
conjecture,  by  means  of  his  sight  only,  how  many  inches 
or  feet  they  were  in  length,  breadth,  or  thickness.  He 
could  perceive  little  or  nothing  of  their  real  figure  ;  not 
could  he  discern  that  this  was  a  cube,  that  a  sphere;  that 
this  was  a  cone,  and  that  a  cylinder.  His  eye  could 
not  inform  him  that  this  object  was  near,  and  that  more 
remote.  The  habit  of  a  man  or  of  a  woman,  which 
appeared  to  us  of  one  uniform  colour,  variously  folded 
and  shaded,  would  present  to  his  eye  neither  fold  nor 
shade,  but  variety  of  colour.  In  a  word,  his  eyes, 
though  ever  so  perfect,  would  at  first  give  him  almost  no 
information  of  things  without  him.  They  would  indeed 
present  the  same  appearances  to  him  as  they  do  to  us, 
and  speak  the  same  language  ;  but  to  him  it  is  an  un- 
known language;  and,  therefore,  he  would  attend  only 
to  the  signs,  without  knowing  the  signification  of  them, 
whereas  to  us  it  is  a  language  perfectly  familiar  ;  and, 
therefore,  we  take  no  notice  of  the  signs,  but  attend 
only  to  the  thing  signified  by  them. 

Section  IV. 

THAT  COLOUR   IS   A   QUALITY   OF   BODIES,    NOT   A   SENSATION 
OF   THE    MIND. 

BY  colour,  all  men,  who  have  not  been  tutored  by 
modern  philosophy,  understand,  not  a  sensation  of  the 
mind,  which  can  have  no  existence  when  it  is  not  per- 
ceived, but  a  quality  or  modification  of  bodies,  which 
continues  to  be  the  same  whether  it  is  seen  -or  not. 
The  scarlet-rose  which  is  before  me,  is  still  a  scarlet-rose 
when  I  shut  my  eyes,  and  was  so  at  midnight  when  no 
eye  saw  it.  The  colour  remains  when  the  appearance 
ceases;  it  remains  the  same  when  the  appearance 
changes.  For  when  I  view  this  scarlet-rose  through 
a  pair  of  green  spectacles,  the  appearance  is  changed; 


174  THE  PHILOSOPHY  OF  REID.  [CH.V1. 

but  I  do  not  conceive  the  colour  of  the  rose  changed. 
To  a  person  in  the  jaundice,  it  has  still  another  appear- 
ance; but  he  is  easily  convinced  that  the  change  is  in  his 
eye,  and  not  in  the  colour  of  the  object.  Every  differ- 
ent degree  of  light  makes  it  have  a  different  appearance, 
and  total  darkness  takes  away  all  appearance,  but  makes 
not  the  least  change  in  the  colour  of  the  body.  We  may, 
by  a  variety  of  optical  experiments,  change  the  appear- 
ance of  figure  and  magnitude  in  a  body,  as  well  as  that 
of  colour;  we  may  make  one  body  appear  to  be  ten. 
But  all  men  believe,  that,  as  a  multiplying  glass  does  not 
really  produce  ten  guineas  out  of  one,  nor  a  microscope 
turn  a  guinea  into  a  ten-pound  piece,  so  neither  does  a 
coloured  glass  change  the  real  colour  of  the  object  seen 
through  it,  when  it  changes  the  appearance  of  that  col- 
our. 

The  common  language  of  mankind  shews  evidently, 
that  we  ought  to  distinguish  between  the  colour  of  a 
body,  which  is  conceived  to  be  a  fixed  and  permanent 
quality  in  the  body,  and  the  appearance  of  that  colour 
to  the  eye,  which  may  be  varied  a  thousand  ways,  by  a 
variation  of  the  light,  of  the  medium,  or  of  the  eye  it- 
self. The  permanent  colour  of  the  body  is  the  cause 
which,  by  the  mediation  of  various  kinds  or  degrees  of 
light,  and  of  various  transparent  bodies  interposed,  pro- 
duces all  this  variety  of  appearances.  When  a  coloured 
body  is  presented,  there  is  a  certain  apparition  to  the  eye, 
or  to  the  mind,  which  we  have  called  the  appearance  of  col- 
our. Mr.  Locke  calls  it  an  idea;  and,  indeed,  it  may  be 
called  so  with  the  greatest  propriety.  This  idea  can 
have  no  existence  but  when  it  is  perceived.  It  is  a  kind 
of  thought,  and  can  only  be  the  act  of  a  percipient  or 
thinking  being.  By  the  constitution  of  our  nature,  we 
are  led  to  conceive  this  idea  as  a  sign  of  something  ex- 
ternal, and  are  impatient  till  we  learn  its  meaning.  A 
thousand  experiments  for  this  purpose  are  made  every 
day  by  children,  even  before  they  come  to  the  use  of  rea- 


SEC.  IV.]  THE  PHILOSOPHY  OF  REID.  175 

son.  They  look  at  things,  they  handle  them,  they  put 
them  in  various  positions,  at  different  distances,  and  in 
different  lights.  The  ideas  of  sight,  by  these  means, 
come  to  be  associated  with,  and  readily  to  suggest,  things 
external,  and  altogether  unlike  them.  In  particular, 
that  idea  which  we  have  called  the  appearance  of  colour, 
suggests  the  conception  and  belief  of  some  unknown 
quality  in  the  body  which  occasions  the  idea;  and  it  is 
to  this  quality,  and  not  to  the  idea,  that  we  give  the 
name  of  colour.  *  The  various  colours,  although  in  their 
nature  equally  unknown,  are  easily  distinguished  when 
we  think  or  speak  of  them,  by  being  associated  with  the 
ideas  which  they  excite.  In  like  manner,  gravity,  mag- 
netism, and  electricity,  although  all  unknown  qualities, 
are  distinguished  by  their  different  effects.  As  we  grow 
up,  the  mind  acquires  a  habit  of  passing  so  rapidly  from 
the  ideas  of  sight  to  the  external  things  suggested  by 
them,  that  the  ideas  are  not  in  the  least  attended  to,  nor 
have  they  names  given  them  in  common  language. 

When  we  think  or  speak  of  any  particular  colour, 
however  simple  the  notion  may  seem  to  be  which  is  pre- 
sented to  the  imagination,  it  is  really  in  some  sort  com- 
pounded. It  involves  an  unknown  cause  and  a  known 
effect.  The  name  of  colour  belongs  indeed  to  the  cause 
only,  and  not  to  the  effect.  But  as  the  cause  is  unknown, 
we  can  form  no  distinct  conception  of  it  but  by  its  rela- 
tion to  the  known  effect;  and,  therefore,  both  go  together 
in  the  imagination,  and  are  so  closely  united,  that  they 
are  mistaken  for  one  simple  object  of  thought*  When  I 

*  It  is  justly  observed  by  Mr.  Stewart,  that  these  passages  seem 
inconsistent  with  each  other.  If  in  the  perception  of  colour,  the  sen- 
sation and  the  quality  "be  so  closely  united  as  to  be  mistaken  for 
one  simple  object  of  thought,"  does  it  not  obviously  follow,  that  it 
is  to  this  compounded  notion  the  name  of  colour  must  in  general  be 
given  ?  On  the  other  hand,  when  it  is  said  that  the  name  of  colour  is 
never  given  to  the  sensation,  btit  to  the  quality  onfy,  does  not  this 
imply,  that  every  time  the  word  is  pronounced,  the  quality  is  sepa- 
rated from  the  sensation,  even  in  the  imagination  of  the  vulgar  ?— H. 


176  THE  PHILOSOPHY  OF  REID.  tCn.Vl. 

would  conceive  those  colours  of  bodies  which  we  call  scar- 
let and  blue — if  I  conceived  them  only  as  unknown  quali- 
ties, I  could  perceive  no  distinction  between  the  one 
and  the  other.  I  must,  therefore,  for  the  sake  of  dis- 
tinction, join  to  each  of  them,  in  my  imagination,  some 
effect  or  some  relation  that  is  peculiar;  and  the  most 
obvious  distinction  is,  the  appearance  which  one  and  the 
other  makes  to  the  eye.  Hence  the  appearance  is,  in 
the  imagination,  so  closely  united  with  the  quality  called 
a  scarlet-colour,  that  they  are  apt  to  be  mistaken  for  one 
and  the  same  thing,  although  they  are  in  reality  so  differ- 
ent and  'so  unlike,  that  one  is  an  idea  in  the  mind,  and  the 
other  is  a  quality  of  body. 

I  conclude,  then,  that  colour  is  not  a  sensation,  but  a 
secondary  quality  of  bodies,  in  the  sense  we  have  already 
explained;  that  it  is  a  certain  power  or  virtue  in  bodies, 
that  in  fair  daylight  exhibits  to  the  eye  an  appearance 
which  is  very  familiar  to  us,  although  it  hath  no  name. 
Colour  differs  from  other  secondary  qualities  in  this, 
that,  whereas  the  name  of  the  quality  is  sometimes  given 
to  the  sensation  which  indicates  it,  and  is  occasioned  by 
it,  we  never,  as  far  as  I  can  judge,  give  the  name  of  col- 
our to  the  sensation,  but  to  the  quality  only.  *  Perhaps 
the  reason  of  this  may  be,,  that  the  appearances  of  the 
same  colour  are  so  various  and  changeable,  according  to 
the  different  modifications  of  the  light,  of  the  medium, 
and  of  the  eye,  that  language  could  not  afford  names  for 
them.  And,  indeed,  they  are  so  little  interesting  that 
they  are  never  attended  to,  but  serve  only  as  signs  to  in- 
troduce the  things  signified  by  them.  Nor  ought  it  to 
appear  incredible,  that  appearances  so  frequent  and  so 
familiar  should  have  no  names,  nor  be  made  objects  of 
thought;  since  we  have  before  shewn  that  this  is  true  of 
many  sensations  of  touch,  which  are  no  less  frequent  nor 
less  familiar. 

*  See  note  on  p.  175. 


SEC.  V.]  THE  PHILOSOPHY   OF   REID.  177 

Section   V. 

AN   INFERENCE  .FROM   THE    PRECEDING. 

From  what  hath  been  said  about  colour,  we  may  in- 
fer two  things.  The  first  is,  that  one  of  the  most  re- 
markable paradoxes  of  modern  philosophy,  which  hath 
been  universally  esteemed  as  a  great  discovery,  is,  in 
reality,  when  examined  to  the  bottom,  nothing  else  but 
an  abuse  of  words.  The  paradox  I  mean  is,  That  col- 
our is  not  a  quality  of  bodies,  but  only  an  idea  in  the 
mind.  We  have  shewn,  that  the  word  colour,  as  used  by 
the  vulgar,  cannot  signify  an  idea  in  the  mind,  but  a 
permanent  quality  of  body.  We  have  shewn  that  there  is 
really  a  permanent  quality  of  body,  to  which  the  common 
use  of  this  word  exactly  agrees.  Can  any  stronger  proof 
be  desired,  that  this  quality  is  that  to  which  the  vulgar 
give  the  name  of  colour?  If  it  should  be  said,  that  this 
quality,  to  which  we  give  the  name  of  colour,  is  unknown 
to  the  vulgar,  and,  therefore,  can  have  no  name  among 
them,  I  answer,  it  is,  indeed,  known  only  by  its  effects 
— that  is,  by  its  exciting  a  certain  idea  in  us;  but  are 
there  not  numberless  qualities  of  bodies  which  are  known 
only  by  their  effects,  to  which,  notwithstanding,  we  find 
it  necessary  to  give  names  ?  Medicine  alone  might  fur- 
nish us  with  a  hundred  instances  of  this  kind.  Do  not 
the  words  astringent,  narcotic,  epispastic,  caustic,  and  innu- 
merable others,  signify  qualities  of  bodies,  which  are 
known  only  by  their  effects  upon  animal  bodies  ?  Why, 
then,  should  not  the  vulgar  give  a  name  to  a  quality, 
whose  effects  are  every  moment  perceived  by  their  eyes  ? 
We  have  all  the  reason,  therefore,  that  the  nature  of  the 
thing  admits,  to  think  that  the  vulgar  apply  the  name  of 
colour  to  that  quality  of  bodies  which  excites  in  us  what 
the  philosophers  call  the  idea  of  colour.  And  that 
there  is  such  a  quality  in  bodies,  all  philosophers 


178  THE  PHILOSOPHY   OF  REID.  [Cn.  VI. 

allow,  who  allow  that  there  is  any  such  thing  as  body. 
Philosophers  have  thought  fit  to  leave  that  quality  of 
bodies  which  the  vulgar  call  colour,  without  a  name,  and 
to  give  the  name  of  colour  to  the  idea  or  appearance,  to 
which,  as  we  have  shewn,  the  vulgar  give  no  name,  be- 
cause they  never  make  it  an  object  of  thought  or  reflec- 
tion. Hence  it  appears,  that  when  philosophers  affirm 
that  colour  is  not  in  bodies,  but  in  the  mind,  and  the 
vulgar  affirm  that  colour  is  not  in  the  mind,  but  is  a 
quality  of  bodies,  there  is  no  difference  between  them 
about  things,  but  only  about  the  meaning  of  a  word. 

The  vulgar  have  undoubted  right  to  give  names  to 
things  which  they  are  daily  conversant  about;  and  phi- 
losophers seem  justly  chargeable  with  an  abuse  of  lan- 
guage, when  they  change  the  meaning  of  a  common 
word,  without  giving  warning. 

If  it  is  a  good  rule,  to  think  with  philosophers  and 
speak  with  the  vulgar,  it  must  be  right  to  speak  with  the 
vulgar  when  we  think  with  them,  and  not  to  shock  them 
by  philosophical  paradoxes,  which,  when  put  into  com- 
mon language,  express  only  the  common  sense  of  man- 
kind. 

If  you  ask  a  man  that  is  no  philosopher,  what  colour 
is,  or  what  makes  one  body  appear  white,  another  scar- 
let, he  cannot  tell.  He  leaves  that  inquiry  to  philos- 
ophers, and  can  embrace  any  hypothesis  about  it,  ex- 
cept that  of  our  modern  philosophers,  who  affirm  that 
colour  is  not  in  body,  but  only  in  the  mind. 

Nothing  appears  more  shocking  to  his  apprehension, 
than  that  visible  objects  should  have  no  colour,  and  that 
colour  should  be  in  that  which  he  conceives  to  be  invisi- 
ble. Vet  this  strange  paradox  is  not  only  universally  re- 
ceived, but  considered  as  one  of  the  noblest  discoveries 
of  modern  philosophy.  The  ingenious  Addison,  in  the 
Spectator,  No.  413,  speaks  thus  of  it: — "I  have  here 
supposed  that  my  reader  is  acquainted  with  that  great 
modern  discovery,  which  is  at  present  universally  ac- 


SEC.V.]  THE  PHILOSOPHY  OF  REID.  179 

knowledged  by  all  the  inquirers  into  natural  philoso- 
phy— namely,  that  light  and  colours,  as  apprehended 
by  the  imagination,  are  only  ideas  in  the  mind,  and  not 
qualities  that  have  any  existence  in  matter.  As  this  is  a 
truth  which  has  been  proved  incontestably  by  many 
modern  philosophers,  and  is,  indeed,  one  of  the  finest 
speculations  in  that  science,  if  the  English  reader  would 
see  the  notion  explained  at  large,  he  may  find  it  in  the 
eighth  chapter  of  the  second  book  of  Locke's  Essay  on 
Human  Understanding.'" 

Mr.  Locke  and  Mr.  Addison  are  writers  who  have  de- 
served so  well  of  mankind,  that  one  must  feel  some  un- 
easiness in  differing  from  them,  and  would  wish  to 
ascribe  all  the  merit  that  is  due  to  a  discovery  upon 
which  they  put  so  high  a  value.  And,  indeed,  it  is  just 
to  acknowledge  that  Locke,  and  other  modern  philoso- 
phers, on  the  subject  of  secondary  qualities,  have  the 
merit  of  distinguishing  more  accurately  than  those  that 
went  before  them,  between  the  sensation  in  the  mind, 
and  that  constitution  or  quality  of  bodies  which  gives 
occasion  to  the  sensation.  They  have  shewn  clearly 
that  these  two  things  are  not  only  distinct,  but  altogether 
unlike:  that  there  is  no  similitude  between  the  effluvia  of 
an  odorous  body  and  the  sensation  of  smell,  or  between 
the  vibrations  of  a  sounding  body  and  the  sensation  of 
sound:  that  there  can  be  no  resemblance  between  the 
feeling  of  heat,  and  the  constitution  of  the  heated  body 
which  occasions  it;  or  between  the  appearance  which  a 
coloured  body  makes  to  the  eye,  and  the  texture  of  the 
body  which  causes  that  appearance. 

Nor  was  the  merit  small  of  distinguishing  these  things 
accurately;  because,  however  different  and  unlike  in 
their  nature,  they  have  been  always  so  associated  in'  the 
imagination,  as  to  coalesce,  as  it  were,  into  one  two- 
faced  form,  which,  from  its  amphibious  nature,  could 
not  justly  be  appropriated  either  to  body  or  mind;  and, 
until  it  was  properly  distinguished  into  its  different  con- 


180  THE  PHILOSOPHY  OF  REID.  [Cn.  VI. 

stituent  parts,  it  was  impossible  to  assign  to  either  their 
just  shares  in  it.  None  of  the  ancient  philosophers  had 
made  this  distinction.  *  The  followers  of  Democritus  and 
Epicurus  conceived  the  forms  of  heat,  and  sound,  and 
colour,  to  be  in  the  mind  only;  but  that  our  senses  fal- 
laciously represented  them  as  being  in  bodies.  The 
Peripatetics  imagined  that  those  forms  are  really  in 
bodies;  and  that  the  images  of  them  are  conveyed  to  the 
mind  by  our  senses,  f 

The  one  system  made  the  senses  naturally  fallacious 
and  deceitful;  the  other  made  the  qualities  of  body  to 
resemble  the  sensations  of  the  mind.  Nor  was  it  possi- 
ble to  find  a  third,  without  making  the  distinction  we 
have  mentioned;  by  which,  indeed,  the  errors  of  both 
these  ancient  systems  are  avoided,  and  we  are  not  left 
under  the  hard  necessity  of  believing^  either,  on  the  one 
hand,  that  our  sensations  are  like  to  the  qualities  of 
body,  or,  on  the  other,  that  God  hath  given  us  one  faculty 
to  deceive  us,  and  another  to  detect  the  cheat. 

We  desire,  therefore,  with  pleasure,  to  do  justice  to 
the  doctrine  of  Locke,  and  other  modern  philosophers, 
with  regard  to  colour  and  other  secondary  qualities,  and 
to  ascribe  to  it  its  due  merit,  while  we  beg  leave  to  cen- 
sure the  language  in  which  they  have  expressed  their 
doctrine.  When  they  had  explained  and  established  the 
distinction  between  the  appearance  which  colour  makes 
to  the  eye,  and  the  modification  of  the  coloured  body 
which,  by  the  laws  of  nature,  causes  that  appearance, 
the  question  was,  whether  to  give  the  name  of  colour  to 


*  This  is  inaccurate.  The  distinction  was  known  to  the  ancient 
philosophers;  and  Democritus  was  generally  allowed  to  be  its  author. 
This  Reid  himself  elsewhere  indeed  admits. — (See  above,  pp.  140 
156,  '57).-H. 

\  These  statements  concerning  both  classes  of  philosophers  are 
vague  and  incorrect.  The  latter,  in  general,  only  allowed  species 
for  two  senses,  Sight  and  Hearing;  few  admitted  them  in  Feeling; 
and  some  rejected  them  altogether. — H. 


SEC.  VI.J  THE  PHILOSOPHY  OF  REID.  l8l 

the  cause  or  to  the  effect  ?  By  giving  it,  as  they  have 
done,  to  the  effect,  they  set  philosophy  apparently  in 
opposition  to  common  sense,  and  expose  it  to  the  ridi- 
cule of  the  vulgar.  But  had  they  given  the  name  of 
colour  to  the  cause,  as  they  ought  to  have  done,  they 
must  then  have  affirmed,  with  the  vulgar,  that  colour  is 
a  quality  of  bodies;  and  that  there  is  neither  colour  nor 
anything  like  it  in  the  mind.  Their  language,  as  well 
as  their  sentiments,  would  have  been  perfectly  agreeable 
to  the  common  apprehensions  of  mankind,  and  true 
Philosophy  would  have  joined  hands  with  Common 
Sense.  As  Locke  was  no  enemy  to  common  sense,  it 
may  be  presumed,  that,  in  this  instance,  as  in  some 
others,  he  was  seduced  by  some  received  hypothesis;  and 
that  this  was  actually  the  case,  will  appear  in  the  follow- 
ing section. 

Section  VI. 

THAT  NONE  OF  OUR  SENSATIONS  ARE  RESEMBLANCES  OF  ANT 
OF  THE  QUALITIES  OF  BODIES. 

A  second  inference  is,  that,  although  colour  is  really 
a  quality  of  body,  yet  it  is  not  represented  to  the  mind 
by  an  idea  or  sensation  that  resembles  it;  on  the  contrary, 
it  is  suggested  by  an  idea  which  does  not  in  the  least 
resemble  it.  And  this  inference  is  applicable,  not  to 
colour  only,  but  to  all  the  qualities  of  body  which  we 
have  examined. 

It  deserves  to  be  remarked,  that,  in  the  analysis  we 
have  hitherto  given  of  the  operations  of  the  five  senses, 
and  of  the  qualities  of  bodies  discovered  by  them,  no  in- 
stance hath  occurred,  either  of  any  sensation  which  re- 
sembles any  quality  of  body,  or  of  any  quality  of  body 
whose  image  or  resemblance  is  conveyed  to  the  mind  by 
means  of  the  senses. 

There  is  no  phenomenon  in  nature  more  unaccounta- 
ble than  the  intercourse  that  is  camacbSfiStfcfen  the 


0?  THE 

niXTlBSXT 


182  THE  PHILOSOPHY  OF  REIDc  [CH,  VI. 

mind  and  the  external  world — there  is  no  phenomenon 
which  philosophical  spirits  have  shewn  greater  avidity  to 
pry  into,  and  to  resolve.  It  is  agreed  by  all,  that  this 
intercourse  is  carried  on  by  means  of  the  senses;  and  this 
satisfies  the  vulgar  curiosity,  but  not  the  philosophic. 
Philosophers  must  have  some  system,  some  hypothesis, 
that  shews  the  manner  in  which  our  senses  make  us 
acquainted  with  external  things.  All  the  fertility  of 
human  invention  seems  to  have  produced  only  one  hy- 
pothesis for  this  purpose,  which,  therefore,  hath  been 
universally  received;  and  that  is,  that  the  mind,  like  a 
mirror,  receives  the  images  of  things  from  without,  by 
means  of  the  senses:  so  that  their  use  must  be  to  con- 
vey these  images  into  the  mind.  * 

Whether  to  these  images  of  external  things  in  the 
mind,  we  give  the  name  of  sensible  forms,  or  sensible 
species,  with  the  Peripatetics,  or  the  name  of  ideas  of  sen- 
sation, with  Locke;  or  whether,  with  later  philosophers, 
we  distinguish  sensations,  which  are  immediately  conveyed 
by  the  senses,  from  ideas  of  sensation,  which  are  faint 
copies  of  our  sensations  retained  in  the>  memory  and  im- 
agination ;  f  these  are  only  differences  about  words.  The 
hypothesis  I  have  mentioned  is  common  to  all  these 
different  systems. 

The  necessary  and  allowed  consequence  of  this  hypoth- 
esis is,  that  no  material  thing,  nor  any  quality  of  material 
things,  can  be  conceived  by  us,  or  made  an  object  of  thought, 
until  its  image  is  conveyed  to  the  mind  by  means  of  the  senses. 
We  shall  examine  this  hypothesis  particularly  afterwards, 
and  at  this  time  only  observe,  that,  in  consequence 

*  This  is  incorrect,  especially  as  it  asserts  that  the  one  universal 
hypothesis  of  philosophy  was,  that  "the  mind  receives  the  images  of 
things  from  without,"  meaning  by  these  images,  immediate  or  rep- 
resentative objects,  different  from  the  modifications  of  the  thinking 
subject  itself.— H. 

f  He  refers  to  Hume;  Aristotle,  however,  and  Hobbes,  had  pre- 
viously called  Imagination  a  decaying  sense. — H. 


SEC.  VI.]  THE  PHILOSOPHY   OF   REID.  183 

of  it,  one  would  naturally  expect,  that  to  every  quality 
and  attribute  of  body  we  know  or  can  conceive,  there 
should  be  a  sensation  corresponding,  which  is  the  image 
and  resemblance  of  that  quality;  and  that  the  sensations 
which  have  no  similitude  or  resemblance  to  body,  or  to 
any  of  its  qualities,  should  give  us  no  conception  of  a 
material  world,  or  of  anything  belonging  to  it  These 
things  might  be  expected  as  the  natural  consequences  of 
the  hypothesis  we  have  mentioned. 

Now,  we  have  considered,  in  this  and  the  preceding 
chapters,  Extension,  Figure,  Solidity,  Motion,  Hardness, 
Roughness,  as  well  as  Colour,  Heat,  and  Cold,  Sound, 
Taste,  and  Smell.  We  have  endeavoured  to  shew  that 
our  nature  and  constitution  lead  us  to  conceive  these  as 
qualities  of  body,  as  all  mankind  have  always  conceived 
them  to  be.  We  have  likewise  examined  with  great  at- 
tention the  various  sensations  we  have  by  means  of  the 
five  senses,  and  are  not  able  to  find  among  them  all  one 
single  image  of  body,  or  of  any  of  its  qualities.  From 
whence,  then,  come  those  images  of  body  and  of  its  qual- 
ities into  the  mind,?  Let  philosophers  resolve  this  ques- 
tion. All  I  can  say  is,  that  they  come  not  by  the  senses. 
I  am  sure  that,  by  proper  attention  and  care,  I  may 
know  my  sensations,  and  be  able  to  affirm  with  certainty 
what  they  resemble,  and  what  they  do  not  resemble.  I 
have  examined  them  one  by  one,  and  compared  them 
with  matter  and  its  qualities;  and  I  cannot  find  one  of 
them  that  confesses  a  resembling  feature. 

A  truth  so  evident  as  this — that  our  sensations  are  not 
images  of  matter,  or  of  any  of  its  qualities — ought  not  to 
yield  to  a  hypothesis  such  as  that  above-mentioned,  how- 
ever ancient,  or  however  universally  received  by  philos- 
ophers ;  nor  can  there  be  any  amicable  union  between  the 
two.  This  will  appear  by  some  reflections  upon  the 
spirit  of  the  ancient  and  modern  philosophy  concerning 
sensation. 

During  the  reign  of  the  Peripatetic  philosophy,  our 


1 84  THE  PHILOSOPHY   OF   REID.  [CH.  VI. 

sensations  were  not  minutely  or  accurately  examined. 
The  attention  of  philosophers,  as  well  as  of  the  vulgar, 
was  turned  to  the  things  signified  by  them:  therefore,  in 
consequence  of  the  common  hypothesis,  it  was  taken  for 
granted,  that  all  the  sensations  we  have  from  external 
things,  are  the  forms  or  images  of  these  external  things. 
And  thus  the  truth  we  have  mentioned  yielded  entirely  to 
the  hypothesis,  and  was  altogether  suppressed  by  it. 

Des  Cartes  gave  a  noble  example  of  turning  our 
attention  inward,  and  scrutinizing  our  sensations;  and 
this  example  hath  been  very  worthily  followed  by  modern 
philosophers,  particularly  by  Malebranche,  Locke,  Berke- 
ley, and  Hume.  The  effect  of  this  scrutiny  hath  been, 
a  gradual  discovery  of  the  truth  above-mentioned — to 
wit,  the  dissimilitude  between  the  sensations  of  our  minds, 
and  the  qualities  or  attributes  of  an  insentient  inert  sub- 
stance, such  as  we  conceive  matter  to  be.  But  this 
valuable  and  useful  discovery,  in  its  different  stages,  hath 
still  been  unhappily  united  to  the  ancient  hypothesis — 
and  from  this  inauspicious  match  of  opinions,  so  un- 
friendly and  discordant  in  their  natures,  have  arisen  those 
monsters  of  paradox  and  scepticism  with  which  the 
modern  philosophy  is  too  justly  chargeable. 

Locke  saw  clearly,  and  proved  incontestably,  that  the 
sensations  we  have  by  taste,  smell,  and  hearing,  as  well 
as  the  sensations  of  colour,  heat,  and  cold,  are  not 
resemblances  of  anything  in  bodies;  and  in  this  he  agrees 
with  Des  Cartes  and  Malebranche.  Joining  this  opinion 
with  the  hypothesis,  it  follows  necessarily,  that  three 
senses  of  the  five  are  cut  off  from  giving  us  any  intelligence 
of  the  material  world,  as  being  altogether  inept  for  that 
office.  Smell,  and  taste,  and  sound,  as  well  as  colour 
and  heat,  can  have  no  more  relation  to  body,  than  anger 
or  gratitude  ;  nor  ought  the  former  to  be  called  qualities 
of  body,  whether  primary  or  secondary,  any  more  than 
the  latter.  For  it  was  natural  and  obvious  to  argue  thus 
from  that  hypothesis:  If  heat,  and  colour,  and  sound 


SEC.  VI.]  THE  PHILOSOPHY  OF  REID.  185 

are  real  qualities  of  body,  the  sensations  by  which  we 
perceive  them  must  be  resemblances  of  those  qualities  ; 
but  these  sensations  are  not  resemblances ;  therefore, 
those  are  not  real  qualities  of  body. 

We  see,  then,  that  Locke,  having  found  that  the  ideas 
of  secondary  qualities  are  no  resemblances,  was  com- 
pelled, by  a  hypothesis  common  to  all  philosophers,  to 
deny  that  they  are  real  qualities  of  body.  It  is  more 
difficult  to  assign  a  reason  why,  after  this,  he  should  call 
them  secondary  qualities;  for  this  name,  if  I  mistake  not, 
was  of  his  invention.*  Surely  he  did  not  mean  that  they 
were  secondary  qualities  of  the  mind ;  and  I  do  not  see 
with  what  propriety,  or  even  by  what  tolerable  license, 
he  could  call  them  secondary  qualities  of  body,  after 
finding  that  they  were  no  qualities  of  body  at  all.  In 
this,  he  seems  to  have  sacrificed  to  Common  Sense,  and 
to  have  been  led  by  her  authority  even  in  opposition  to 
his  hypothesis.  The  same  sovereign  mistress  of  our 
opinions  that  led  this  philosopher  to  call  those  things 
secondary  qualities  of  body,  which,  according  to  his 
principles  and  reasonings,  were  no  qualities  of  body  at 
all,  hath  led,  not  the  vulgar  of  all  ages  only,  but  philoso- 
phers also,  and  even  the  disciples  of  Locke,  to  believe 
them  to  be  real  qualities  of  body — she  hath  led  them  to 
investigate,  by  experiments,  the  nature  of  colour,  and 
sound,  and  heat,  in  bodies.  Nor  hath  this  investigation 
been  fruitless,  as  it  must  have  been  if  there  had  been  no 
such  thing  in  bodies  ;  on  the  contrary,  it  hath  produced 
very  noble  and  useful  discoveries,  which  make  a  very 
considerable  part  of  natural  philosophy.  If,  then,  natural 
philosophy  be  not  a  dream,  there  is  something  in  bodies 
which  we  call  colour,  and  heat,  and  sound.  And  if  this 

*  The  terms  First  and  Second^  or  Primary  and  Secondary  qualities, 
were  no  more  an  invention  of  Locke  than  the  distinction  which  he 
applied  them  to  denote.  The  terms  First  and  Second  Qualities,  as  I 
have  noticed,  in  the  Aristotelian  philosophy,  marked  out,  however, 
a  different  distribution  of  qualities  than  that  in  question. — H. 


1 86  THE  PHILOSOPHY  OF  REID.  [Cn.  VI. 

be  so,  the  hypothesis  from  which  the  contrary  is  con- 
cluded, must  be  false :  for  the  argument,  leading  to  a 
false  conclusion,  recoils  against  the  hypothesis  from 
which  it  was  drawn,  and  thus  directs  its  force  backward. 
If  the  qualities  of  body  were  known  to  us  only  by 
sensations  that  resemble  them,  then  colour,  and  sound, 
and  heat  could  be  no  qualities  of  body;  but  these  are  real 
qualities  of  body  ;  and,  therefore,  the  qualities  of  body 
are  not  known  only  by  means  of  sensations  that  resemble 
them. 

But  to  proceed.  What  Locke  had  proved  with  regard 
to  the  sensations  we  have  by  smell,  taste,  and  hearing, 
Bishop  Berkeley  proved  no  less  unanswerably  with  regard 
to  all  our  other  sensations  ;  to  wit,  that  none  of  them 
can  in  the  least  resemble  the  qualities  of  a  lifeless  and 
insentient  being,  such  as  matter  is  conceived  to  be. 
Mr.  Hume  hath  confirmed  this  by  his  authority  and 
reasoning.  This  opinion  surely  looks  with  a  very  malign 
aspect  upon  the  old  hypothesis  ;  yet  that  hypothesis  hath 
still  been  retained,  and  conjoined  with  it.  And  what  a 
brood  of  monsters  hath  this  produced ! 

The  first-born  of  this  union,  and,  perhaps,  the  most 
harmless,  was,  that  the  secondary  qualities  of  body  were 
mere  sensations  of  the  mind.  To  pass  by  Malebranche's 
notion  of  seeing  all  things  in  the  ideas  of  the  divine  mind, 
as  a  foreigner,  never  naturalized  in  this  island ;  the  next 
was  Berkeley's  system,  That  extension,  and  figure,  and 
hardness,  and  motion — that  land,  and  sea,  and  houses, 
and  our  own  bodies,  as  well  as  those  of  our  wives,  and 
children,  and  friends — are  nothing  but  ideas  of  the  mind: 
and  that  there  is  nothing  existing  in  nature,  but  minds 
and  ideas. 

The  progeny  that  followed,  is  still  more  frightful  ;  so 
that  it  is  surprising,  that  one  could  be  found  who  had 
the  courage  to  act  the  midwife,  to  rear  it  up,  and  to 
usher  it  into  the  world.  No  causes  nor  effects  ;  no  sub- 
stances, material  or  spiritual ;  no  evidence,  even  in 


SEC.  VII.]  THE  PHILOSOPHY  OF  REID.  187 

mathematical  demonstration ;  no  liberty  nor  active  power ; 
nothing  existing  in  nature,  but  impressions  and  ideas 
following  each  other,  without  time,  place,  or  subject. 
Surely  no  age  ever  produced  such  a  system  of  opinions, 
justly  deduced  with  great  acuteness,  perspicuity,  and  ele- 
gance, from  a  principle  universally  received.  The  hy- 
pothesis we  have  mentioned  is  the  father  of  them  all. 
The  dissimilitude  of  our  sensations  and  feelings  to  ex- 
ternal things,  is  the  innocent  mother  of  most  of  them. 

As  it  happens  sometimes,  in  an  arithmetical  operation, 
that  two  errors  balance  one  another,  so  that  the  con- 
clusion is  little  or  nothing  affected  by  them;  but  when 
one  of  them  is  corrected,  and  the  other  left,  we  are  led 
farther  from  the  truth  than  by  both  together:  so  it  seems 
to  have  happened  in  the  Peripatetic  philosophy  of 
sensation,  compared  with  the  modern.  The  Peripatetics 
adopted  two  errors;  but  the  last  served  as  a  corrective  to 
the  first,  and  rendered  it  mild  and  gentle ;  so  that  their 
system  had  no  tendency  to  scepticism.  The  moderns 
have  retained  the  first  of  those  errors,  but  have  gradually 
detected  and  corrected  the  last.  The  consequence  hath 
been,  that  the  light  we  have  struck  out  hath  created 
darkness,  and  scepticism  hath  advanced  hand  in  hand 
with  knowledge,  spreading  its  melancholy  gloom,  first 
over  the  material  worjd,  and  at  last  over  the  whole  face 
of  nature.  Such  a  phenomenon  as  this,  is  apt  to  stagger 
even  the  lovers  of  light  and  knowledge,  while  its  cause  is 
latent ;  but,  when  that  is  detected,  it  may  give  hopes  that 
this  darkness  shall  not  be  everlasting,  but  that  it  shall  be 
succeeded  by  a  more  permanent  light. 

Section  VIL 

OF   VISIBLE    FIGURE    AND    EXTENSION. 

Although  there  is  no  resemblance,  nor,  as  far  as  we 
know,  any  necessary  connection,  between  that  quality  in 
a  body  which  we  call  its  colour,  and  the  appearance  which 


1 88  THE  PHILOSOPHY  OF  REID.  [CH.  VI 

that  colour  makes  to  the  eye,  it  is  quite  otherwise  with 
regard  to  its  figure  and  magnitude.  There  is  certainly  a 
resemblance,  and  a  necessary  connection,  between  the 
visible  figure  and  magnitude  of  a  body,  and  its  real  figure 
and  magnitude ;  no  man  can  give  a  reason  why  a  scarlet 
colour  affects  the  eye  in  the  manner  it  does  ;  no  man  can 
be  sure  that  it  affects  his  eye  in  the  same  manner  as  it 
affects  the  eye  of  another,  and  that  it  has  the  same  ap- 
pearance to  him  as  it  has  to  another  man  ; — but  we  can 
assign  a  reason  why  a  circle  placed  obliquely  to  the  eye, 
should  appear  in  the  form  of  an  ellipse.  The  visible 
figure,  magnitude,  and  position  may,  by  mathematical 
reasoning,  be  deduced  from  the  real ;  and  it  may  be 
demonstrated,  that  every  eye  that  sees  distinctly  and  per- 
fectly, must,  in  the  same  situation,  see  it  under  this  form, 
and  no  other.  Nay,  we  may  venture  to  affirm,  that  a 
man  born  blind,  if  he  were  instructed  in  mathematics, 
would  be  able  to  determine  the  visible  figure  of  a  body 
when  its  real  figure,  distance,  and  position,  are  given. 
Dr.  Saunderson  understood  the  projection  of  the  sphere, 
and  perspective.  Now,  I  require  no  more  knowledge  in 
a  blind  man,  in  order  to  his  being  able  to  determine  the 
visible  figure  of  bodies,  than  that  he  can  project  the  out- 
line of  a  given  body,  upon  the  surface  of  a  hollow  sphere, 
whose  centre  is  in  the  eye.  This  projection  is  the  visible 
figure  he  wants  :  for  it  is  the  same  figure  with  that  which 
is  projected  upon  the  tunica  retina  in  vision. 

A  blind  man  can  conceive  lines  drawn  from  every 
point  of  the  object  to  the  centre  of  the  eye,  making  an- 
gles. He  can  conceive  that  the  length  of  the  object  will 
appear  greater  or  less,  in  proportion  to  the  angle  which 
it  subtends  at  the  eye ;  and  that,  in  like  manner,  the 
breadth,  and  in  general  the  distance,  of  any  one  point 
of  the  object  from  any  other  point,  will  appear  greater 
or  less,  in  proportion  to  the  angles  which  those  distances 
subtend.  He  can  easily  be  made  to  conceive,  that  the 
visible  appearance  has  no  thickness,  any  more  than  a 


SEC.  VII.]  THE  PHILOSOPHY  OF  REID.  189 

projection  of  the  sphere,  or  a  perspective  draught.  He 
may  be  informed,  that  the  eye,  until  it  is  aided  by  ex- 
perience, does  not  represent  one  object  as  nearer  or  more 
remote  than  another.  Indeed,  he  would  probably  con- 
jecture this  of  himself,  and  be  apt  to  think  that  the  rays 
of  light  must  make  the  same  impression  upon  the  eye, 
whether  they  come  from  a  greater  or  a  less  distance. 

These  are  all  the  principles  which  we  suppose  our 
blind  mathematician  to  have  ;  and  these  he  may  cer- 
tainly acquire  by  information  and  reflection.  It  is  no 
less  certain,  that,  from  these  principles,  having  given  the 
real  figure  and  magnitude  of  a  body,  and  its  position 
and  distance  with  regard  to  the  eye,  he  can  find  out  its 
visible  figure  and  magnitude.  He  can  demonstrate  in 
general,  from  these  principles,  that  the  visible  figure  of 
all  bodies  will  be  the  same  with  that  of  their  projection 
upon  the  surface  of  a  hollow  sphere,  when  the  eye  is 
placed  in  the  centre.  And  he  can  demonstrate  that  their 
visible  magnitude  will  be  greater  or  less,  according  as 
their  projection  occupies  a  greater  or  less  part  of  the 
surface  of  this  sphere. 

To  set  this  matter  in  another  light,  let  us  distinguish 
betwixt  the  position  of  objects  with  regard  to  the  eye,  and 
their  distance  from  it.  Objects  that  lie  in  the  same  right 
line  drawn  from  the  centre  of  the  eye,  have  the  same 
position,  however  different  their  distances  from  the  eye 
may  be  :  but  objects  which  lie  in  different  right  lines 
drawn  from  the  eye's  centre,  have  a  different  position  ; 
and  this  difference  of  position  is  greater  or  less  in  pro- 
portion to  the  angle  made  at  the  eye  by  the  right  lines 
mentioned.  Having  thus  defined  what  we  mean  by  the 
position  of  objects  with  regard  to  the  eye,  it  is  evident 
that,  as  the  real  figure  of  a  body  consists  in  the  situation 
of  its  several  parts  with  regard  to  one  another,  so  its  vis- 
ible figure  consists  in  the  position  of  its  several  parts 
with  regard  to  the  eye ;  and,  as  he  that  hath  a  distinct 
conception  of  the  situation  of  the  parts  of  the  body  with 


190  THE  PHILOSOPHY  OF  REID.  [Cn.  VI. 

regard  to  one  another,  must  have  a  distinct  conception 
of  its  real  figure ;  so  he  that  conceives  distinctly  the 
position  of  its  several  parts  with  regard  to  the  eye,  must 
have  a  distinct  conception  of  its  visible  figure.  Now, 
there  is  nothing,  surely,  to  hinder  a  blind  man  from 
conceiving  the  position  of  the  several  parts  of  a  body 
with  regard  to  the  eye,  any  more  than  from  conceiving 
their  situation  with  regard  to  one  another  ;  and,  there- 
fore, I  conclude,  that  a  blind  man  may  attain  a  distinct 
conception  of  the  visible  figure  of  bodies. 

Although  we  think  the  arguments  that  have  been 
offered  are  sufficient  to  prove  that  a  blind  man  may  con- 
ceive the  visible  extension  and  figure  of  bodies  ;  yet,  in 
order  to  remove  some  prejudices  against  this  truth,  it 
will  be  of  use  to  compare  the  notion  which  a  blind 
mathematician  might  form  to  himself  of  visible  figure, 
with  that  which  is  presented  to  the  eye  in  vision,  and  to 
observe  wherein  they  differ. 

First,  Visible  figure  is  never  presented  to  the  eye  but 
in  conjunction  with  colour  :  and,  although  there  be  no 
connection  between  them  from  the  nature  of  the  things, 
yet,  having  so  invariably  kept  company  together,  we  are 
hardly  able  to  disjoin  them  even  in  our  imagination. 
What  mightily  increases  this  difficulty  is,  that  we  have 
never  been  accustomed  to  make  visible  figure  an  object 
of  thought.  It  is  only  used  as  a  sign,  and,  having 
served  this  purpose,  passes  away,  without  leaving  a  trace 
behind.  The  drawer  or  designer,  whose  business  it  is  to 
hunt  this  fugitive  form,  and  to  take  a  copy  of  it,  finds 
how  difficult  his  task  is,  after  many  years'  labour  and 
practice.  Happy  !  if  at  last  he  can  acquire  the  art  of 
arresting  it  in  his  imagination,  until  he  can  delineate  it. 
For  then  it  is  evident  that  he  must  be  able  to  draw  as 
accurately  from  the  life  as  from  a  copy.  But  how  few 
of  the  professed  masters  of  designing  are  ever  able  to 
arrive  at  this  degree  of  perfection  !  It  is  no  wonder, 
then,  that  we  should  find  so  great  difficulty  in  conceiving 


SBC.  VII.]  THE  PHILOSOPHY  OF  REID.  191 

this  form  apart  from  its  constant  associate,  when  it  is  so 
difficult  to  conceive  it  at  all.  But  our  blind  man's  no- 
tion of  visible  figure  will  not  be  associated  with  colour, 
of  which  he  hath  no  conception,  but  it  will,  perhaps,  be 
associated  with  hardness  or  smoothness,  with  which  he 
is  acquainted  by  touch.  These  different  associations 
are  apt  to  impose  upon  us,  and  to  make  things  seem 
different,  which,  in  reality,  are  the  same. 

Secondly,  The  blind  man  forms  the  notion  of  visible 
figure  to  himself,  by  thought,  and  by  mathematical 
reasoning  from  principles  ;  whereas,  the  man  that  sees, 
has  it  presented  to  his  eye  at  once,  without  any  labour, 
without  any  reasoning,  by  a  kind  of  inspiration.  A 
man  may  form  to  himself  the  notion  of  a  parabola,  or 
a  cycloid,  from  the  mathematical  definition  of  those 
figures,  although  he  had  never  seen  them  drawn  or  de- 
lineated. Another,  who  knows  nothing  of  the  mathe- 
matical definition  of  the  figures,  may  see  them  delineated 
on  paper,  or  feel  them  cut  out  in  wood.  Each  may  have 
a  distinct  conception  of  the  figures,  one  by  mathematical 
reasoning,  the  other  by  sense.  Now,  the  blind  man 
forms  his  notion  of  visible  figure  in  the  same  manner  as 
the  first  of  these  formed  his  notion  of  a  parabola  or  a 
cycloid,  which  he  never  saw. 

Thirdly,  Visible  figure  leads  the  man  that  sees,  directly 
to  the  conception  of  the  real  figure,  of  which  it  is  a  sign. 
But  the  blind  man's  thoughts  move  in  a  contrary  direc- 
tion. For  he  must  first  know  the  real  figure,  distance, 
and  situation  of  the  body,  and  from  thence  he  slowly 
traces  out  the  visible  figure  by  mathematical  reasoning. 
Nor  does  his  nature  lead  him  to  conceive  this  visible 
figure  as  a  sign  ;  it  is  a  creature  of  his  own  reason  and 
imagination. 


Ip2  THE    PHILOSOPHY    OF    REID.  [Cn.  VI. 

Section    VIIL 

SOME    QUERIES    CONCERNING   VISIBLE    FIGURE  ANSWERED. 

It  may  be  asked,  What  kind  of  thing  is  this  visible 
figure  ?  Is  it  a  Sensation,  or  an  Idea  ?  If  it  is  an  idea, 
from  what  sensation  is  it  copied  ?  These  questions  may 
seem  trivial  or  impertinent  to  one  who  does  not  know 
that  there  is  a  tribunal  of  inquisition  erected  by  certain 
modern  philosophers,  before  which  everything  in  nature 
must  answer.  The  articles  of  inquisition  are  few  indeed, 
but  very  dreadful  in  their  consequences.  They  are  only 
these  :  Is  the  prisoner  an  Impression  or  an  Idea  ?  If  an 
idea,  from  what  impression  copied  ?  Now,  if  it  appears 
that  the  prisoner  is  neither  an  impression,  nor  an  idea 
copied  from  some  impression,  immediately,  without 
being  allowed  to  offer  anything  in  arrest  of  judgment,  he 
is  sentenced  to  pass  out  of  existence,  and  to  be,  in  all 
time  to  come,  an  empty  unmeaning  sound,  or  the  ghost 
of  a  departed  entity. 

Before  this  dreadful  tribunal,  cause  and  effect,  time 
and  place,  matter  and  spirit,  have  been  tried  and  cast  : 
how  then  shall  such  a  poor  flimsy  form  as  visible  figure 
stand  before  it  ?  It  must  even  plead  guilty,  and  confess 
that  it  is  neither  an  impression  nor  an  idea.  For,  alas  ! 
it  is  notorious,  that  it  is  extended  in  length  and  breadth  ; 
it  may  be  long  or  short,  broad  or  narrow,  triangular, 
quadrangular,  or  circular;  and,  therefore,  unless  ideas 
and  impressions  are  extended  and  figured,  it  cannot 
belong  to  that  category. 

If  it  should  still  be  asked,  To  what  category  of  beings 
does  visible  figure  then  belong  ?  I  can  only,  in  answer, 
give  some  tokens,  by  which  those  who  are  better  ac- 
quainted with  the  categories,  may  chance  to  find  its 
place.  It  is,  as  we  have  said,  the  position  of  the  several 
parts  of  a  figured  body  with  regard  to  the  eye.  The 


SEC.  VIII.]  THE  PHILOSOPHY  OF  REID.  193 

different  positions  of  the  several  parts  of  the  body  with 
regard  to  the  eye,  when  put  together,  make  a  real  figure, 
which  is  truly  extended  in  length  and  breadth,  and 
which  represents  a  figure  that  is  extended  in  length, 
breadth,  and  thickness.  In  like  manner,  a  projection 
of  the  sphere  is  a  real  figure,  and  hath  length  and 
breadth,  but  represents  the  sphere,  which  hath  three 
dimensions.  A  projection  of  the  sphere,  or  a  perspec- 
tive view  of  a  palace,  is  a  representative  in  the  very  same 
sense  as  visible  figure  is ;  and  wherever  they  have  their 
lodgings  in  the  categories,  this  will  be  found  to  dwell 
next  door  to  them. 

It  may  farther  be  asked,  Whether  there  be  any  sensa- 
tion proper  to  visible  figure,  by  which  it  is  suggested  in 
vision  ? — or  by  what  means  it  is  presented  to  the  mind  ? 
This  is  a  question  of  some  importance,  in  order  to  our 
having  a  distinct  notion  of  the  faculty  of  seeing  :  and  to 
give  all  the  light  to  it  we  can,  it  is  necessary  to  compare 
this  sense  with  other  senses,  and  to  make  some  supposi- 
tions, by  which  we  may  be  enabled  to  distinguish  things 
that  are  apt  to  be  confounded,  although  they  are  totally 
different. 

There  are  three  of  our  senses  which  give  us  intelli- 
gence of  things  at  a  distance:  smell,  hearing,  and  sight. 
In  smelling  and  in  hearing,  we  have  a  sensation  or  im- 
pression upon  the  mind,  which,  by  our  constitution,  we 
conceive  to  be  a  sign  of  something  external :  but  the  po- 
sition of  this  external  thing,  with  regard  to  the  organ  of 
sense,  is  not  presented  to  the  mind  along  with  the  sen- 
sation. When  I  hear  the  sound  of  a  coach,  I  could  not, 
previous  to  experience,  determine  whether  the  sounding 
body  was  above  or  below,  to  the  right  hand  or  to  the 
left.  So  that  the  sensation  suggests  to  me  some  external 
object  as  the  cause  or  occasion  of  it;  but  it  suggests  not 
the  position  of  that  object,  whether  it  lies  in  this  direc- 
tion or  in  that.  The  same  thing  may  be  said  with  regard 
to  smelling.  But  the  case  is  quite  different  with  regard 


194  THE  PHILOSOPHY  OF  REID.  [Cn.  VI. 

to  seeing.  When  I  see  an  object,  the  appearance  which 
the  colour  of  it  makes,  may  be  called  the  sensation,  which 
suggests  to  me  some  external  thing  as  its  cause;  but  it 
suggests  likewise  the  individual  direction  and  position  of 
this  cause  with  regard  to  the  eye.  I  know  it  is  precisely 
in  such  a  direction,  and  in  no  other.  At  the  same  time, 
I  am  not  conscious  of  anything  that  can  be  called  sensa- 
tion, but  the  sensation  of  colour.  The  position  of  the 
coloured  thing  is  no  sensation;  but  it  is  by  the  laws  of 
my  constitution  presented  to  the  mind  along  with  the 
colour,  without  any  additional  sensation. 

Let  us  suppose  that  the  eye  were  so  constituted  that 
the  rays  coming  from  any  one  point  of  the  object  were 
not,  as  they  are  in  our  eyes,  collected  in  one  point  of  the 
retina,\)ut  diffused  over  the  whole:  it  is  evident  to  those 
who  understand  the  structure  of  the  eye,  that  such  an 
eye  as  we  have  supposed,  would  shew  the  colour  of  a 
body  as  our  eyes  do,  but  that  it  would  neither  shew 
figure  nor  position.  The  operation  of  such  an  eye  would 
be  precisely  similar  to  that  of  hearing  and  smell;  it  would 
give  no  perception  of  figure  or  extension,  but  merely  of 
colour.  Nor  is  the  supposition  we  have  made  altogether 
imaginary:  for  it  is  nearly  the  case  of  most  people  who 
have  cataracts,  whose  crystalline,  as  Mr.  Cheselden  ob- 
serves, does  not  altogether  exclude  the  rays  of  light,  but 
diffuses  them  over  the  retina,  so  that  such  persons  see 
things  as  one  does  through  a  glass  of  broken  gelly:  they 
perceive  the  colour,  but  nothing  of  the  figure  or  magni- 
tude of  objects. 

Again,  if  we  should  suppose  that  smell  and  sound 
were  conveyed  in  right  lines  from  the  objects,  and  that 
every  sensation  of  hearing  and  smell  suggested  the  pre- 
cise direction  or  position  of  its  object;  in  this  case,  the 
operations  of  hearing  and  smelling  would  be  similar 
to  that  of  seeing:  we  should  smell  and  hear  the  figure 
of  objects,  in  the  same  sense  as  now  we  see  it;  and 
every  smell  and  sound  would  be  associated  with  some 


SEC.  VIII.]  THE  PHILOSOPHY  OF  REID.  19$ 

figure  in  the  imagination,  as  colour  is  in  our  present 
state. 

We  have  reason  to  believe,  that  the  rays  of  light  make 
some  impression  upon  the  retina;  but  we  are  not  con- 
scious of  this  impression;  nor  have  anatomists  or  philos- 
ophers been  able  to  discover  the  nature  and  effects  of  it; 
whether  it  produces  a  vibration  in  the  nerve,  or  the  mo- 
tion of  some  subtile  fluid  contained  in  the  nerve,  or 
something  different  from  either,  to  which  we  cannot  give 
a  name.  Whatever  it  is,  we  shall  call  it  the  material  im- 
pression ;  remembering  carefully,  that  it  is  not  an  impres- 
sion upon  the  mind,  but  upon  the  body;  and  that  it  is 
no  sensation,  nor  can  resemble  sensation,  any  more  than 
figure  or  motion  can  resemble  thought.  Now,  this  ma- 
terial impression,  made  upon  a  particular  point  of  the 
retina,  by  the  laws  of  our  constitution,  suggests  two 
things  to  the  mind — namely,  the  colour  an  i  the  position 
of  some  external  object.  No  man  can  give  a  reason  why 
the  same  material  impression  might  not  have  suggested 
sound,  or  smell,  or  either  of  these,  along  with  the  posi- 
tion of  the  object.  That  it  should  suggest  colour  and 
position,  and  nothing  else,  we  can  resolve  only  into  our 
constitution,  or  the  will  of  our  Maker.  And  since  there 
is  no  necessary  connection  between  these  two  things  sug- 
gested by  this  material  impression,  it  might,  if  it  had  so 
pleased  our  Creator,  have  suggested  one  of  them  without 
the  other.  Let  us  suppose,  therefore,  since  it  plainly 
appears  to  be  possible,  that  our  eyes  had  been  so  framed 
as  to  suggest  to  us  the  position  of  the  object,  without 
suggesting  colour,  or  any  other  quality:  What  is  the  con- 
sequence of  this  supposition  ?  It  is  evidently  this,  that 
the  person  endued  with  such  an  eye,  would  perceive  the 
visible  figure  of  bodies,  without  having  any  sensation  or 
impression  made  upon  his  mind.  The  figure  he  per- 
ceives is  altogether  external;  and  therefore  cannot  be 
called  an  impression  upon  the  mind,  without  the  gross- 
est abuse  of  language.  If  it  should  be  said,  that  it  is 


196  THE  PHILOSOPHY   OF  REID.  [Cu.  VI. 

impossible  to  perceive  a  figure,  unless  there  be  some  im- 
pression of  it  upon  the  mind,  I  beg  leave  not  to  admit 
the  impossibility  of  this  without  some  proof:  and  I  can 
find  none.  Neither  can  I  conceive  what  is  meant  by  an 
impression  of  figure  upon  the  mind.  I  can  conceive  an 
impression  of  figure  upon  wax,  or  upon  any  body  that  is 
fit  to  receive  it;  but  an  impression  of  it  upon  the  mind,  is 
to  me  quite  unintelligible;  and,  although  I  form  the  most 
distinct  conception  of  the  figure,  I  cannot,  upon  the 
strictest  examination,  find  any  impression  of  it  upon  my 
mind. 

If  we  suppose,  last  of  all,  that  the  eye  hath  the  power 
restored  of  perceiving  colour,  I  apprehend  that  it  will  be 
allowed,  that  now  it  perceives  figure  in  the  very  same 
manner  as  before,  with  this  difference  only,  that  colour 
is  always  joined  with  it. 

In  answer,  therefore,  to  the  question  proposed,  there 
seems  to  be  no  sensation  that  is  appropriated  to  visible 
figure,  or  whose  office  it  is  to  suggest  it.  It  seems  to  be 
suggested  immediately  by  the  material  impression  upon 
the  organ,  of  which  we  are  not  conscious:  and  why  may 
not  a  material  impression  upon  the  retina  suggest  visible 
figure,  as  well  as  the  material  impression  made  upon  the 
hand,  when  we  grasp  a  ball,  suggests  real  figure  ?  In 
the  one  case,  one  and  the  same  material  impression, 
suggests  both  colour  and  visible  figure;  and  in  the  other 
case,  one  and  the  same  material  impression  suggests  hard- 
ness, heat,  or  cold,  and  real  figure,  all  at  the  same 
time. 

We  shall  conclude  this  section  with  another  question 
upon  this  subject.  Since  the  visible  figure  of  bodies  is  a 
real  and  external  object  to  the  eye,  as  their  tangible  fig- 
ure is  to  the  touch,  it  may  be  asked,  Whence  arises  the 
difficulty  of  attending  to  the  first,  and  the  facility  of  at- 
tending to  the  last  ?  It  is  certain  that  the  first  is  more 
frequently  presented  to  the  eye,  than  the  last  is  to  the 
touch;  the  first  is  as  distinct  and  determinate  an  object 


SEC.  VIII.)  THE  PHILOSOPHY   OF   REID.  197 

as  the  last,  and  seems  in  its  own  nature  as  proper  for 
speculation.  Yet  so  little  hath  it  been  attended  to,  that 
it  never  had  a  name  in  any  language,  until  Bishop  Berke- 
ley gave  it  that  which  we  have  used  after  his  example, 
to  distinguish  it  from  the  figure  which  is  the  object  of 
touch. 

The  difficulty  of  attending  to  the  visible  figure  of 
bodies,  and  making  it  an  object  of  thought,  appears  so 
similar  to  that  which  we  find  in  attending  to  our  sensa- 
tions, that  both  have  probably  like  causes.  Nature  in- 
tended the  visible  figure  as  a  sign  of  the  tangible  figure 
and  situation  of  bodies,  and  hath  taught  us,  by  a  kind 
of  instinct,  to  put  it  always  to  this  use.  Hence  it  hap- 
pens, that  the  mind  passes  over  it  with  a  rapid  motion, 
to  attend  to  the  things  signified  by  it.  It  is  as  unnatu- 
ral to  the  mind  to  stop  at  the  visible  figure,  and  attend 
to  it,  as  it  is  to  a  spherical  body  to  stop  upon  an  inclined 
plane.  There  is  an  inward  principle,  which  constantly 
carries  it  forward,  and  which  cannot  be  overcome  but  by 
a  contrary  force. 

There  are  other  external  things  which  nature  intended 
for  signs;  and  we  find  this  common  to  them  all,  that  the 
mind  is  disposed  to  overlook  them,  and  to  attend  only 
to  the  things  signified  by  them.  Thus  there  are  certain 
modifications  of  the  human  face,  which  are  natural  signs 
of  the  present  disposition  of  the  mind.  Every  man  un- 
derstands the  meaning  of  these  signs,  but  not  one  of  a  hun- 
dred ever  attended  to  the  signs  themselves,  or  knows 
anything  about  them.  Hence  you  may  find  many  an  ex- 
cellent practical  physiognomist  who  knows  nothing  of 
the  proportions  of  a  face  nor  can  delineate  or  describe 
the  expression  of  any  one  passion. 

An  excellent  painter  or  statuary  can  tell,  not  only  what 
are  the  proportions  of  a  good  face,  but  what  changes 
every  passion  makes  in  it.  This,  however,  is  one  of  the 
chief  mysteries  of  his  art,  to  the  acquisition  of  which  in- 
finite labour  and  attention,  as  well  as  a  happy  genius, 


198  THE  PHILOSOPHY   OF  REID.  (Cn.  VI. 

are  required  ;  but  when  he  puts  his  art  in  practice,  and 
happily  expresses  a  passion  by  its  proper  signs,  every 
one  understands  the  meaning  of  these  signs,  without  art, 
and  without  reflection. 

What  has  been  said  of  painting,  might  easily  be  ap- 
plied to  all  the  fine  arts.  The  difficulty  in  them  all  con- 
sists in  knowing  and  attending  to  those  natural  signs 
whereof  every  man  understands  the  meaning. 

We  pass  from  the  sign  to  the  thing  signified,  with  ease, 
and  by  natural  impulse  ;  but  to  go  backward  from  the 
thing  signified  to  the  sign,  is  a  work  of  labour  and  diffi- 
culty. Visible  figure,  therefore,  being  intended  by  nature 
to  be  a  sign,  we  pass  on  immediately  to  the  thing  signi- 
fied, and  cannot  easily  return  to  give  any  attention  to  the 
sign. 

Nothing  shews  more  clearly  our  indisposition  to  at- 
tend to  visible  figure  and  visible  extension  than  this — 
that,  although  mathematical  reasoning  is  no  less  appli- 
cable to  them,  than  to  tangible  figure  and  extension,  yet 
they  have  entirely  escaped  the  notice  of  mathematicians. 
While  that  figure  and  that  extension  which  are  objects 
of  touch,  have  been  tortured  ten  thousand  ways  for 
twenty  centuries,  and  a  very  noble  system  of  science  has 
been  drawn  out  of  them,  not  a  single  proposition  do  we 
find  with  regard  to  the  figure  and  extension  which  are 
the  immediate  objects  of  sight  ! 

When  the  geometrician  draws  a  diagram  with  the  most 
perfect  accuracy — when  he  keeps  his  eye  fixed  upon  it, 
while  he  goes  through  a  long  process  of  reasoning,  and 
demonstrates  the  relations  of  the  several  parts  of  his  fig- 
ure— he  does  not  consider  that  the  visible  figure  pre- 
sented to  his  eye,  is  only  the  representative  of  a  tangible 
figure,  upon  which  all  his  attention  is  fixed  ;  he  does  not 
consider  that  these  two  figures  have  really  different  pro- 
perties ;  and  that,  what  he  demonstrates  to  be  true  of 
the  one,  is  not  true  of  the  other. 

This,  perhaps,  will  seem  so  great  a  paradox,  even  to 


SEC.  IX.]  THE  PHILOSOPHY  OF  REID.  199 

mathematicians,  as  to  require  demonstration  before  it 
can  be  believed.  Nor  is  the  demonstration  at  all  difiV 
cult,  if  the  reader  will  have  patience  to  enter  but  a  little 
into  the  mathematical  consideration  of  visible  figure, 
which  we  shall  call  the  geometry  ofvisibles. 


Section  IX. 

OF  THE  GEOMETRY  OF  VISIBLES.* 

In  this  geometry,  the  definitions  of  a  point ;  of  a  line, 
whether  straight  or  curve  ;  of  an  angle,  whether  acute, 
or  right,  or  obtuse;  and  of  a  circle — are  the  same  as  in 
common  geometry.  The  mathematical  reader  will  easily 
enter  into  the  whole  mystery  of  this  geometry,  if  he  at- 
tends duly  to  these  few  evident  principles. 

1.  Supposing  the  eye  placed  in  the  centre  of  a  sphere, 
every  great  circle  of  the  sphere  will   have  the  same    ap- 
pearance to  the  eye  as  if  it  was  a  straight  line  ;  for  the 
curvature  of  the  circle  being  turned  directly  toward  the 
eye,  is  not  perceived  by  it.     And,  for  the  same  reason, 
any  line  which  is  drawn  in  the  plane  of  a  great  circle  of 
the  sphere,  whether  it  be  in  reality  straight  or  curve,  will 
appear  straight  to  the  eye. 

2.  Every  visible  right  line  will  appear  to  coincide  with 
some  great  circle  of  the  sphere  ;  and  the  circumference 
of  that  great  circle,  even  when  it  is  produced  until  it 
returns  into  itself,  will  appear  to  be  a  continuation  of 
the  same  visible  right  line,  all  the  parts  of  it  being  visi- 
bly in  directum.     For  the  eye,  perceiving  only  the  posi- 
tion of  objects  with  regard  to  itself,  and  not  their  dis- 
tance, will  see  those  points  in  the   same   visible  place 
which  have  the  same  position  with  regard  to   the  eye, 

*  How  does  this  differ  from  a  doctrine  of  Perspective  ?— At  any 
rate,  the  notion  is  Berkeley's.  Compare  "New  Theory  of  Vision," 
§§ 


200  THE  PHILOSOPHY   OF  REID.  [Cn.  VI. 

how  different  soever  their  distances  from  it  may  be. 
Now,  since  a  plane  passing  through  the  eye  and  a  given 
visible  right  line,  will  be  the  plane  of  some  great  circle 
of  the  sphere,  every  point  of  the  visible  right  line  will 
have  the  same  position  as  some  point  of  the  great  circle; 
therefore,  they  will  both  have  the  same  visible  place,  and 
coincide  to  the  eye  ;  and  the  whole  circumference  of  the 
great  circle,  continued  even  until  it  returns  into  itself, 
will  appear  to  be  a  continuation  of  the  same  visible  right 
line. 

Hence  it  follows — 

3.  That  every  visible  right  line,  when  it  is  continued 
in  directum,  as  far  as  it  may  be  continued,  will  be  rep- 
resented by  a  great  circle  of  a  sphere,  in  whose  centre 
the  eye  is  placed.     It  follows — 

4.  That  the  visible  angle  comprehended  under  two 
visible  right  lines,  is  equal  to  the  spherical  angle  com- 
prehended under  the  two  great  circles,  which  are  the 
representatives  of  these  visible  lines.     For,  since  the  vis- 
ible lines  appear  to  coincide  with  the  great  circles,   the 
visible  angle  comprehended  under  the  former  must  be 
equal  to  the  visible  angle  comprehended  under  the  latter. 
But  the  visible  angle  comprehended  under  the  two  great 
circles,  when  seen  from  the  centre,  is  of  the  same  mag- 
nitude with  the  spherical  angle  which  they  really  com- 
prehend,  as  mathematicians  know ;  therefore,  the  visi- 
ble angle  made  by  any  two  visible  lines  is  equal  to  the 
spherical  angle  made  by  the  two  great  circles  of  the 
sphere  which  are  their  representatives. 

5.  Hence  it  is  evident,  that  every  visible  right-lined 
triangle  will  coincide  in  all  its  parts  with  some  spherical 
triangle.     The  sides  of  the  one  will  appear  equal  to  the 
sides  of  the  other,  and  the  angles  of  the  one  to  the  an- 
gles of  the  other,  each  to  each  :  and,  therefore,  the  whole 
of  the  one  triangle  will  appear  equal  to  the  whole  of  the 
other.     In  a  word,  to  the  eye  they  will  be  one  and  the 
same,  and  have  the  same  mathematical  properties.     The 


SEC.  IX.)  THE  PHILOSOPHY  OF  REID.  2OI 

properties,  therefore,  of  visible  right-lined  triangles  are 
not  the  same  with  the  properties  of  plain  triangles,  but 
are  the  same  with  those  of  spherical  triangles. 

6.  Every  lesser  circle  of  the  sphere  will  appear  a  cir- 
cle to  the  eye,  placed,  as  we  have  supposed  all  along,   in 
the  centre  of  the  sphere ;  and,  on  the  other  hand,  every 
visible  circle  will  appear  to  coincide  with  some  lesser  cir- 
cle of  the  sphere. 

7.  Moreover,  the  whole  surface  of  the  sphere  will  rep- 
resent the  whole  of  visible  space  ;  for,  since  every  visible 
point  coincides  with  some  point  of  the  surface  of  the 
sphere,  and  has  the  same  visible  place,  it  follows,  that  all 
the  parts  of  the  spherical  surface  taken  together,  will 
represent  all  possible  visible  places — that  is,  the  whole 
of  visible  space.     And  from  this  it  follows,  in  the  last 
place — 

8.  That  every  visible  figure  will  be  represented  by  that 
part  of  the  surface  of  the  sphere  on  which  it  might  be 
projected,  the  eye  being  in  the  centre.     And  every  such 
visible  figure  will  bear  the  same  ratio  to  the  whole  of  visi- 
ble space,  as  the  part  of  the  spherical  surface  which  rep- 
resents it,  bears  to  the  whole  spherical  surface. 

The  mathematical  reader,  I  hope,  will  enter  into  these 
principles  with  perfect  facility,  and  will  as  easily  per- 
ceive that  the  following  propositions  with  regard  to  visi- 
ble figure  and  space,  which  we  offer  only  as  a  specimen, 
may  be  mathematically  demonstrated  from  them,  and  are 
not  less  true  nor  less  evident  than  the  propositions  of 
Euclid,  with  regard  to  tangible  figures. 

Prop.  i.  Every  right  line  being  produced,  will  at  last 
return  into  itself. 

2.  A  right  line    returning  into  itself,  is  the  longest 
possible  right  line  ;  and  all  other  right  lines  bear  a  finite 
ratio  to  it. 

3.  A  right  line  returning  into  itself,  divides   the  whole 
of  visible  space  into  two  equal  parts,  which  will  both  be 
comprehended  under  this  right  line. 


202  THE  PHILOSOPHY  OF  REID.  (Ca.  VI. 

4.  The  whole  of  visible  space  bears  a  finite  ratio  to 
any  part  of  it. 

5.  Any  two  right  lines  being  produced,  will  meet  in 
two  points,  and  mutually  bisect  each  other. 

6.  If  two  lines  be  parallel — that  is,  everywhere  equally 
distant  from  each  other — they  cannot  both  be  straight. 

7.  Any  right  line  being  given,  a  point  may  be  found, 
which  is  at  the  same  distance  from  all  the  points  of  the 
given  right  line. 

8.  A  circle  may  be  parallel  to  a  right  line — that  is, 
may  be  equally  distant  from  it  in  all  its  parts. 

9.  Right-lined    triangles   that   are   similar,    are    also 
equal. 

10.  Of  every  right-lined  triangle,  the  three  angles  taken 
together,  are  greater  than  two  right  angles. 

11.  The  angles  of  a  right-lined  [triangle,  may  all  be 
right  angles,  or  all  obtuse  angles. 

12.  Unequal  circles  are  not  as  the  squares  of  their 
diameters,  nor  are  their  circumferences  in  the  ratio  of 
their  diameters. 

This  small  specimen  of  the  geometry  of  visibles,  is  in- 
tended to  lead  the  reader  to  a  clear  and  distinct  con- 
ception of  the  figure  and  extension  which  is  presented  to 
the  mind  by  vision  ;  and  to  demonstrate  the  truth  of 
what  we  have  affirmed  above — namely,  that  those  figures 
and  that  extension  which  are  the  immediate  objects  of 
sight,  are  not  the  figures  and  the  extension  about  which 
common  geometry  is  employed  ;  that  the  geometrician, 
while  he  looks  at  his  diagram,  and  demonstrates  a 
proposition,  hath  a  figure  presented  to  his  eye,  which  is 
only  a  sign  and  representative  of  a  tangible  figure  :  that 
he  gives  not  the  least  attention  to  the  first,  but  attends 
only  to  the  last  ;  and  that  these  two  figures  have  differ- 
ent properties,  so  that  what  he  demonstrates  of  the  one, 
is  not  true  of  the  other. 

It  deserves,  however,  to  be  remarked,  that,  as  a  small 
part  of  a  spherical  surface  differs  not  sensibly  from  a 


SEC.  IX.  THE  PHILOSOPHY  OF  REIt).  2O3 

plain  surface,  so  a  small  part  of  visible  extension  differs 
very  little  from  that  extension  in  length  and  breadth, 
which  is  the  object  of  touch.  And  it  is  likewise  to  be  ob- 
served, that  the  human  eye  is  so  formed,  that  an  object 
which  is  seen  distinctly  and  at  one  view,  can  occupy  but 
a  small  part  of  visible  space  ;  for  we  never  see  distinctly 
what  is  at  a  considerable  distance  from  the  axis  of  the 
eye  ;  and,  therefore,  when  we  would  see  a  large  object 
at  one  view,  the  eye  must  be  at  so  great  a  distance,  that 
the  object  occupies  but  a  small  part  of  visible  space. 
From  these  two  observations,  it  follows,  that  plain  fig- 
ures which  are  seen  at  one  view,  when  their  planes  are 
not  oblique,  but  direct  to  the  eye,  differ  little  from  the 
visible  figures  which  they  present  to  the  eye.  The  sev- 
eral lines  in  the  tangible  figure,  have  very  nearly  the  same 
proportion  to  each  other  as  in  the  visible  ;  and  the  an- 
gles of  the  one  are  very  nearly,  although  not  strictly  and 
mathematically,  equal  to  those  of  the  other.  Although, 
therefore,  we  have  found  many  instances  of  natural  signs 
which  have  no  similitude  to  the  things  signified,  this  is 
not  the  case  with  regard  to  visible  figure.  It  hath,  in 
all  cases,  such  a  similitude  to  the  thing  signified  by  it, 
as  a  plan  or  profile  hath  to  that  which  it  represents  ; 
and,  in  some  cases,  the  sign  and  thing  signified  have  to 
all  sense  the  same  figure  and  the  same  proportions.  If 
we  could  find  a  being  endued  with  sight  only,  without 
any  other  external  sense,  and  capable  of  reflecting  and 
reasoning  upon  what  he  sees,  the  notions  and  philoso- 
phical speculations  of  such  a  being,  might  assist  us  in 
the  difficult  task  of  distinguishing  the  perceptions  which 
we  have  purely  by  sight,  from  those  which  derive  their 
origin  from  other  senses.  Let  us  suppose  such  a  being, 
and  conceive,  as  well  as  we  can,  what  notion  he  would 
have  of  visible  objects,  and  what  conclusions  he  would 
deduce  from  them.  We  must  not  conceive  him  dis- 
posed by  his  constitution,  as  we  are,  to  consider  the 
visible  appearance  as  a  sign  of  something  else  :  it  is  no 


204  THE  PHILOSOPHY   OF   REID.  |CH.  VI. 

sign  to  him,  because  there  is  nothing  signified  by  it ;  and, 
therefore,  we  must  suppose  him  as  much  disposed  to  at- 
tend to  the  visible  figure  and  extension  of  bodies,  as  we 
are  disposed  to  attend  to  their  tangible  figure  and  ex- 
tension. 

If  various  figures  were  presented  to  his  sense,  he 
might,  without  doubt,  as  they  grow  familiar,  compare 
them  together,  and  perceive  wherein  they  agree,  and 
wherein  they  differ.  He  might  perceive  visible  objects 
to  have  length  and  breadth,  but  could  have  no  notion  of 
a  third  dimension,  any  more  than  we  can  have  of  a  fourth. 
All  visible  objects  would  appear  to  be  terminated  by 
lines,  straight  or  curve;  and  objects  terminated  by  the 
same  visible  lines,  would  occupy  the  same  place,  and 
fill  the  same  part  of  visible  space.  It  would  not  be 
possible  for  him  to  conceive  one  object  to  be  be- 
hind another,  or  one  to  be  nearer,  another  more  dis- 
tant. 

To  us,  who  conceive  three  dimensions,  a  line  may  be 
conceived  straight;  or  it  may  be  conceived  incurvated  in 
one  dimension,  and  straight  in  another;  or,  lastly,  it  may 
be  incurvated  in  two  dimensions.  Suppose  a  line  to  be 
drawn  upwards  and  downwards,  its  length  makes  one 
dimension,  which  we  shall  call  upwards  and  downwards; 
and  there  are  two  dimensions  remaining,  according  to 
which  it  may  be  straight  or  curve.  It  may  be  bent  to 
the  right  or  to  the  left,  and,  if  it  has  no  bending  either 
to  right  or  left,  it  is  straight  in  this  dimension.  But 
supposing  it  straight  in  this  dimension  of  right  and  left, 
there  is  still  another  dimension  remaining,  in  which  it 
may  be  curve;  for  it  may  be  bent  backwards  or  forwards. 
When  we  conceive  a  tangible  straight  line,  we  exclude 
curvature  in  either  of  these  two  dimensions:  and  as  what  is 
conceived  to  be  excluded,  must  be  conceived,  as  well  as 
what  is  conceived  to  be  included,  it  follows  that  all  the 
three  dimensions  enter  into  our  conception  of  a  straight 
line.  Its  length  is  one  dimension,  its  straightnessintwo 


SfiC.  IX.)  THE  PHILOSOPHY  OF  REID.  205 

other  dimensions  is  included,  or  curvature  in  these  two 
dimensions  excluded,  in  the  conception  of  it. 

The  being  we  have  supposed,  having  no  conception 
of  more  than  two  dimensions,  of  which  the  length  of  a 
line  is  one,  cannot  possibly  conceive  it  either  straight  or 
curve  in  more  than  one  dimension;  so  that,  in  his  con- 
ception of  a  right  line,  curvature  to  the  right  hand  or 
left  is  excluded;  but  curvature  backwards  or  forwards 
cannot  be  excluded,  because  he  neither  hath,  nor  can 
have  any  conception  of  such  curvature.  Hence  we  see 
the  reason  that  a  line  which  is  straight  to  the  eye,  may 
return  into  itself;  for  its  being  straight  to  the  eye,  implies 
only  straightness  in  one  dimension;  and  a  line  which  is 
straight  in  one  dimension  may,  notwithstanding,  be 
curve  in  another  dimension,  and  so  may  return  into  it- 
self. 

To  us,  who  conceive  three  dimensions,  a  surface  is 
that  which  hath  length  and  breadth,  excluding  thickness; 
and  a  surface  may  be  either  plain  in  this  third  dimension, 
or  it  may  be  incurvated:  so  that  the  notion  of  a  third 
dimension  enters  into  our  conception  of  a  surface;  for  it 
is  only  by  means  of  this  third  dimension  that  we  can 
distinguish  surfaces  into  plain  and  curve  surfaces;  and 
neither  one  nor  the  other  can  be  conceived  without  con- 
ceiving a  third  dimension. 

The  being  we  have  supposed,  having  no  conception 
of  a  third  dimension,  his  visible  figures  have  length  and 
breadth  indeed;  but  thickness  is  neither  included  nor  ex- 
cluded, being  a  thing  of  which  he  has  no  conception. 
And,  therefore,  visible  figures,  although  they  have  length 
and  breadth,  as  surfaces  have,  yet  they  are  neither  plain 
surfaces  nor  curve  surfaces.  For  a  curve  surface  implies 
curvature  in  a  third  dimension,  and  a  plain  surface  im- 
plies the  want  of  curvature  in  a  third  dimension;  and 
such  a  being  can  conceive  neither  of  these,  because  he 
has  no  conception  of  a  third  dimension.  Moreover,  al- 
though he  hath  a  distinct  conception  of  the  inclination 


206  THE  PHILOSOPHY  OF  REID.  [Cn.  VI. 

of  two  lines  which  make  an  angle,  yet  he  can  neither 
conceive  "a  plain  angle  nor  a  spherical  angle.  Even 
his  notion  of  a  point  is  somewhat  less  determined  than 
ours.  In  the  notion  of  a  point,  we  exclude  length, 
breadth,  and  thickness;  he  excludes  length  and  breadth, 
but  cannot  either  exclude,  or  include  thickness,  because 
he  hath  no  conception  of  it. 

Having  thus  settled  the  notions  which  such  a  being 
as  we  have  supposed  might  form  of  mathematical  points, 
lines,  angles,  and  figures,  it  is  easy  to  see,  that,  by  com- 
paring these  together,  and  reasoning  about  them,  he 
might  discover  their  relations,  and  form  geometrical 
conclusions  built  upon  self-evident  principles.  He 
might  likewise,  without  doubt,  have  the  same  notions 
of  numbers  as  we  have,  and  form  a  system  of  arithmetic. 
It  is  not  material  to  say  in  what  order  he  might  proceed 
in  such  discoveries,  or  how  much  time  and  pains  he 
might  employ  about  them,  but  what  such  a  being,  by  rea- 
son and  ingenuity,  without  any  materials  of  sensation 
but  those  of  sight  only,  might  discover. 

As  it  is  more  difficult  to  attend  to  a  detail  of  possibilities 
than  of  facts,  even  of  slender  authority,  I  shall  beg  leave 
to  give  an  extract  from  the  travels  of  Johannes  Rudolphus 
Anepigraphus,  a  Rosicrucian  philosopher,  who  having, 
by  deep  study  of  the  occult  sciences,  acquired  the  art  of 
transporting  himself  to  various  sublunary  regions,  and 
of  conversing  with  various  orders  of  intelligences,  in  the 
course  of  his  adventures  became  acquainted  with  an  or- 
der of  beings  exactly  such  as  I  have  supposed. 

How  they  communicate  their  sentiments  to  one  an- 
other, and  by  what  means  he  became  acquainted  with 
their  language,  and  was  initiated  into  their  philosophy; 
as  well  as  of  many  other  particulars,  which  might  have 
gratified  the  curiosity  of  his  readers,  and,  perhaps,  added 
credibility  to  his  relation,  he  hath  not  thought  fit  to  in- 
form us;  these  being  matters  proper  for  adepts  only  to 
know. 


SEC.  tX.]  THE  PHILOSOPHY  OF  REID.  207 

His  account  of  their  philosophy  is  as  follows: — 
' '  The  Idomenians, "  saith  he,  "  are  many  of  them  very 
ingenious,  and  much  given  to  contemplation.  In  arith- 
metic, geometry,  metaphysics,  and  physics,  they  have 
most  elaborate  systems.  In  the  two  latter,  indeed,  they 
have  had  many  disputes  carried  on  with  great  subtilty, 
and  are  divided  into  various  sects;  yet  in  the  two  former 
there  hath  been  no  less  unanimity  than  among  the  hu- 
man species.  Their  principles  relating  to  numbers  and 
arithmetic,  making  allowance  for  their  notation,  differ  in 
nothing  from  ours — but  their  geometry  differs  very  con- 
siderably. " 

As  our  author's  account  of  the  geometry  of  the  Ido- 
menians agrees  in  everything  with  the  geometry  of  visibles, 
of  which  we  have  already  given  a  specimen,  we  shall  pass 
over  it.  He  goes  on  thus: — "Colour,  extension,  and  fig- 
ure, are  conceived  to  be  the  essential  properties  of  body.  A 
very  considerable  sect  maintains,  that  colour  is  the  essence 
of  body.  If  there  had  been  no  colour,  say  they,  there 
had  been  no  perception  or  sensation.  Colour  is  all 
that  we  perceive,  or  can  conceive,  that  is  peculiar  to 
body;  extension  and  figure  being  modes  common  to 
body  and  to  empty  space.  And  if  we  should  suppose  a 
body  to  be  annihilated,  colour  is  the  only  thing  in  it  that 
can  be  annihilated;  for  its  place,  and  consequently  the  fig- 
ure and  extension  of  that  place,  must  remain,  and  can- 
not be  imagined  not  to  exist.  These  philosophers  hold 
space  to  be  the  place  of  all  bodies,  immovable  and  in- 
destructible, without  figure  and  similar  in  all  its  parts, 
incapable  of  increase  or  diminution,  yet  not  unmeasura- 
ble;  for  every  the  least  part  of  space  bears  a  finite  ratio  to 
the  whole.  So  that  with  them  the  whole  extent  of  space 
is  the  common  and  natural  measure  of  everything  that 
hath  length  and  breadth;  and  the  magnitude  of  every 
body  and  of  every  figure  is  expressed  by  its  being  such  a 
part  of  the  universe.  In  like  manner,  the  common  and 
natural  measure  of  length  is  an  infinite  right  line,  which, 


208  THE  PHILOSOPHY  OF  REID.  [Cn.  VI. 

as  hath  been  before  observed,  returns  into  itself,  and  hath 
no  limits,  but  bears  a  finite  ratio  to  every  other  line. 

"  As  to  their  natural  philosophy,  it  is  now  acknow- 
ledged by  the  wisest  of  them  to  have  been  for  many  ages 
in  a  very  low  state.  The  philosophers  observing,  that 
body  can  differ  from  another  only  in  colour,  figure,  or 
magnitude,  it  was  taken  for  granted,  that  all  their  particu- 
lar qualities  must  arise  from  the  various  combinations  of 
these  their  essential  attributes;  and,  therefore,  it  was 
looked  upon  as  the  end  of  natural  philosophy,  to  shew 
how  the  various  combinations  of  these  three  qualities  in 
different  bodies  produced  all  the  phenomena  of  nature. 
It  were  endless  to  enumerate  the  various  systems  that 
were  invented  with  this  view,  and  the  disputes  that  were 
carried  on  for  ages;  the  followers  of  every  system  ex- 
posing the  weak  sides  of  other  systems,  and  palliating 
those  of  their  own  with  great  art. 

"At  last,  some  free  and  facetious  spirits,  wearied  with 
eternal  disputation,  and  the  labour  of  patching  and 
propping  weak  systems,  began  to  complain  of  the  sub- 
tilty  of  nature;  of  the  infinite  changes  that  bodies  under- 
go in  figure,  colour,  and  magnitude;  and  of  the  difficulty 
of  accounting  for  these  appearances — making  this  a  pre- 
tence for  giving  up  all  inquiries  into  the  causes  of  things, 
as  vain  and  fruitless. 

"  These  wits  had  ample  matter  of  mirth  and  ridicule 
in  the  systems  of  philosophers;  and,  finding  it  an  easier 
task  to  pull  down  than  to  build  or  support,  and  that 
every  sect  furnished  them  with  arms  and  auxiliaries  to 
destroy  another,  they  began  to  spread  mightily,  and 
went  on  with  great  success.  Thus  philosophy  gave  way 
to  scepticism  and  irony,  and  those  systems  which  had 
been  the  work  of  ages,  and  the  admiration  of  the  learned, 
became  the  jest  of  the  vulgar:  for  even  the  vulgar  readily 
took  part  in  the  triumph  over  a  kind  of  learning  which 
they  had  long  suspected,  because  it  produced  nothing 
but  wrangling  and  altercation.  The  wits,  having  now 


SEC.  IX.]  THE  PHILOSOPHY   OF  REID.  209 

acquired  great  reputation,  and  being  flushed  with  suc- 
cess, began  to  think  their  triumph  incomplete,  until 
every  pretence  to  knowledge  was  overturned  ;  and  ac- 
cordingly began  their  attacks  upon  arithmetic,  geometry, 
and  even  upon  the  common  notions  of  untaught  Ido- 
menians.  So  difficult  it  hath  always  been,"  says 
our  author,  "for  great  conquerors  to  know  where  to 
stop. 

' '  In  the  meantime,  natural  philosophy  began  to  rise 
from  its  ashes,  under  the  direction  of  a  person  of  great 
genius,  who  is  looked  upon  as  having  had  something  in 
him  above  Idomenian  nature.  He  observed,  that  the 
Idomenian  faculties  were  certainly  intended  for  con- 
templation, and  that  the  works  of  nature  were  a  nobler 
subject  to  exercise  them  upon,  than  the  follies  of  systems, 
or  the  errors  of  the  learned  ;  and  being  sensible  of  the 
difficulty  of  rinding  out  the  causes  of  natural  things,  he 
proposed,  by  accurate  observation  of  the  phenomena  of 
nature,  to  find  out  the  rules  according  to  which  they 
happen,  without  inquiring  into  the  causes  of  those  rules. 
In  this  he  made  considerable  progress  himself,  and 
planned  out  much  work  for  his  followers,  who  call  them- 
selves inductive  philosophers.  The  sceptics  look  with  envy 
upon  this  rising  sect,  as  eclipsing  their  reputation,  and 
threatening  to  limit  their  empire;  but  they  are  at  a  loss 
on  what  hand  to  attack  it.  The  vulgar  begin  to  reverence 
it  as  producing  useful  discoveries. 

"It  is  to  be  observed,  that  every  Idomenian  firmly 
believes,  that  two  or  more  bodies  may  exist  in  the  same 
place.  For  this  they  have  the  testimony  of  sense,  and 
they  can  no  more  doubt  of  it,  than  they  can  doubt 
whether  they  have  any  perception  at  all.  They  often  see 
two  bodies  meet  and  coincide  in  the  same  place,  and 
separate  again,  without  having  undergone  any  change  in 
their  sensible  qualities  by  this  penetration.  When  two 
bodies  meet,  and  occupy  the  same  place,  commonly  one 
only  appears  in  that  place,  and  the  other  disappears. 


210  THE  PHILOSOPHY   OF  REID.  [CH.  VI. 

That  which  continues  to  appear  is  said  to  overcome,  the 
other  to  be  overcome. " 

To  this  quality  of  bodies  they  gave  a  name,  which  our 
author  tells  us  hath  no  word  answering  to  it  in  any  hu- 
man language.  And,  therefore,  after  making  a  long 
apology,  which  I  omit,  he  begs  leave  to  call  it  the  over- 
coming quality  of  bodies.  He  assures  us,  that  "  the  spec- 
ulations which  had  been  raised  about  this  single  quality 
of  bodies,  and  the  hypotheses  contrived  to  account  for 
it,  were  sufficient  to  fill  many  volumes.  Nor  have  there 
been  fewer  hypotheses  invented  by  their  philosophers,  to 
account  for  the  changes  of  magnitude  and  figure;  which, 
in  most  bodies  that  move,  they  perceive  to  be  in  a 
continual  fluctuation.  The  founder  of  the  inductive  sect, 
believing  it  to  be  above  the  reach  of  Idomenian  faculties, 
to  discover  the  real  causes  of  these  phenomena,  applied 
himself  to  find  from  observation,  by  what  laws  they  are 
connected  together ;  and  discovered  many  mathematical 
ratios  and  relations  concerning  the  motions,  magnitudes, 
figures,  and  overcoming  quality  of  bodies,  which  con- 
stant experience  confirms.  But  the  opposers  of  this 
sect  choose  rather  to  content  themselves  with  feigned 
causes  of  these  phaenomena,  than  to  acknowledge  the 
real  laws  whereby  they  are  governed,  which  humble  their 
pride,  by  being  confessedly  unaccountable." 

Thus  far  Johannes  Rudolphus  Anepigraphus.  Whe- 
ther this  Anepigraphus  be  the  same  who  is  recorded 
among  the  Greek  alchemistical  writers  not  yet  published, 
by  Borrichius,  Fabricius,  and  others,  I  do  not  pretend 
to  determine.  The  identity  of  their  name,  and  the  simil- 
itude of  their  studies,  although  no  slight  arguments,  yet 
are  not  absolutely  conclusive.  Nor  will  I  take  upon  me 
to  judge  of  the  narrative  of  this  learned  traveller,  by  the 
external  marks  of  his  credibility  ;  I  shall  confine  myself 
to  those  which  the  critics  call  internal  It  would  even 
be  of  small  importance  to  inquire,  whether  the  Idome- 
mans  have  a  real,  or  only  an  ideal  existence;  since  this 


SEC.  X.]  THE  PHILOSOPHY  OF  REID.  211 

is  disputed  among  the  learned  with  regard  to  things  with 
which  we  are  more  nearly  connected.  The  important 
question  is,  whether  the  account  above  given,  is  a  just 
account  of  their  geometry  and  philosophy  ?  We  have  all 
the  faculties  which  they  have,  with  the  addition  of  others 
which  they  have  not;  we  may,  therefore,  form  some 
judgment  of  their  philosophy  and  geometry,  by  separat- 
ing from  all  others,  the  perceptions  we  have  by  sight  and 
reasoning  upon  them.  As  far  as  I  am  able  to  judge  in 
this  way,  after  a  careful  examination,  their  geometry 
must  be  such  as  Anepigraphus  hath  described.  Nor 
does  his  account  of  their  philosophy  appear  to  contain 
any  evident  marks  of  imposture;  although  here,  no 
doubt,  proper  allowance  is  to  be  made  for  liberties 
which  travellers  take,  as  well  as  for  involuntary  mistakes 
which  they  are  apt  to  fall  into. 


Section  X. 

OF  THE  PARALLEL  MOTION  OF  THE  EYES. 

Having  explained,  as  distinctly  as  we  can,  visible  fig- 
ure, and  shewn  its  connection  with  the  things  signified 
by  it,  it  will  be  proper  next  to  consider  some  phaenom- 
ena  of  the  eyes,  and  of  vision,  which  have  commonly 
been  referred  to  custom,  to  anatomical  or  to  mechanical 
causes  ;  but  which,  as  I  conceive,  must  be  resolved  into 
original  powers  and  principles  of  the  human  mind  ;  and, 
therefore,  belong  properly  to  the  subject  of  this  inquiry. 

The  first  is  the  parallel  motion  of  the  eyes ;  by  which, 
when  one  eye  is  turned  to  the  right  or  to  the  left,  up- 
wards or  downwards,  or  straight  forwards,  the  other  al- 
ways goes  along  with  it  in  the  same  direction.  We  see 
plainly,  when  both  eyes  are  open,  that  they  are  always 
turned  the  same  way,  as  if  both  were  acted  upon  by  the 
§ame  motive  force  ;  and  if  one  eye  is  shut,  and  the  hand 


212  THE  PHILOSOPHY   OF  REID.  [Cn.  VI. 

laid  upon  it,  while  the  other  turns  various  ways,  we  feel 
the  eye  that  is  shut  turn  at  the  same  time,  and  that  whether 
we  will  or  not.  What  makes  this  phenomenon  surprising 
is,  that  it  is  acknowledged,  by  all  anatomists,  that  the 
muscles  which  move  the  two  eyes,  and  the  nerves  which 
serve  these  muscles,  are  entirely  distinct  and  unconnected. 
It  would  be  thought  very  surprising  and  unaccountable 
to  see  a  man,  who,  from  his  birth,  never  moved  one 
arm,  without  moving  the  other  precisely  in  the  same 
manner,  so  as  to  keep  them  always  parallel — yet  it* 
would  not  be  more  difficult  to  find  the  physical  cause  of 
such  motion  of  the  arms,  than  it  is  to  find  the  cause  of 
the  parallel  motion  of  the  eyes,  which  is  perfectly  simi- 
lar. 

The  only  cause  that  hath  been  assigned  of  this  parallel 
motion  of  the  eyes,  is  custom.  We  find  by  experience, 
it  is  said,  when  we  begin  to  look  at  objects,  that,  in 
order  to  have  distinct  vision,  it  is  necessary  to  turn  both 
eyes  the  same  way  ;  therefore,  we  soon  acquire  the  habit 
of  doing  it  constantly,  and  by  degrees  lose  the  power  of 
doing  otherwise. 

This  account  of  the  matter  seems  to  be  insufficient ; 
because  habits  are  not  got  at  once  ;  it  takes  time  to  ac- 
quire and  to  confirm  them  ;  and  if  this  motion  of  the 
eyes  were  got  by  habit,  we  should  see  children,  when 
they  are  born,  turn  their  eyes  different  ways,  and  move 
one  without  the  other,  as  they  do  their  hands  or  legs. 
I  know  some  have  affirmed  that  they  are  apt  to  do  so. 
But  I  have  never  found  it  true  from  my  own  observation, 
although  I  have  taken  pains  to  make  observations  of 
this  kind,  and  have  had  good  opportunities.  I  have 
likewise  consulted  experienced  midwives,  mothers,  and 
nurses,  and  found  them  agree,  that  they  had  never  ob- 
served distortions  of  this  kind  in  the  eyes  of  children, 
but  when  they  had  reason  to  suspect  convulsions,  or 
some  preternatural  cause. 

It  seems,  therefore,  to  be  extremely  probable,  that, 


SEC.  X.]  THE  PHILOSOPHY  OF   REID.  213 

previous  to  custom,  there  is  something  in  the  constitu- 
tion, some  natural  instinct,  which  directs  us  to  move 
both  eyes  always  the  same  way. 

We  know  not  how  the  mind  acts  upon  the  body,  nor 
by  what  power  the  muscles  are  contracted  and  relaxed — 
but  we  see  that,  in  some  of  the  voluntary,  as  well  as  in 
some  of  the  involuntary  motions,  this  power  is  so  di- 
rected, that  many  muscles  which  have  no  material  tie 
or  connection,  act  in  concert,  each  of  them  being  taught 
to  play  its  part  in  exact  time  and  measure.  Nor  doth  a 
company  of  expert  players  in  a  theatrical  performance, 
or  of  excellent  musicians  in  a  concert,  or  of  good  dancers 
in  a  country  dance,  with  more  regularity  and  order, 
conspire  and  contribute  their  several  parts,  to  produce 
one  uniform  effect,  than  a  number  of  muscles  do,  in 
many  of  the  animal  functions,  and  in  many  voluntary 
actions.  Yet  we  see  such  actions  no  less  skilfully 
and  regularly  performed  in  children,  and  in  those  who 
know  not  that  they  have  such  muscles,  than  in  the  most 
skilful  anatomist  and  physiologist. 

Who  taught  all  the  muscles  that  are  concerned  in 
sucking,  in  swallowing  our  food,  in  breathing,  and  in 
the  several  natural  expulsions,  to  act  their  part  in  such 
regular  order  and  exact  measure  ?  It  was  not  custom 
surely.  It  was  that  same  powerful  and  wise  Being  who 
made  the  fabric  of  the  human  body,  and  fixed  the  laws 
by  which  the  mind  operates  upon  every  part  of  it,  so  that 
they  may  answer  the  purposes  intended  by  them.  And 
when  we  see,  in  so  many  other  instances,  a  system  of 
unconnected  muscles  conspiring  so  wonderfully  in  their 
several  functions,  without  the  aid  of  habit,  it  needs 
not  be  thought  strange,  that  the  muscles  of  the  eyes 
should,  without  this  aid,  conspire  to  give  that  direction 
to  the  eyes,  without  which  they  could  not  answer  their 
end. 

We  see  :.  like  conspiring  action  in  the  muscles  which 
contract  the  pupils  of  the  two  eyes  ;  and  in  those  mus- 


214  THE  PHILOSOPHY  OF  REID.  [CH.  VI. 

cles,  whatever  they  be,  by  which  the  conformation  of 
the  eyes  is  varied  according  to  the  distance  of  objects. 

It  ought,  however,  to  be  observed,  that,  although  it 
appears  to  be  by  natural  instinct  that  both  eyes  are  al- 
ways turned  the  same  way,  there  is  still  some  latitude 
left  for  custom. 

What  we  have  said  of  the  parallel  motion  of  the  eyes, 
is  not  to  be  understood  so  strictly  as  if  nature  directed 
us  to  keep  their  axes  always  precisely  and  mathemati- 
cally parallel  to  each  other.  Indeed,  although  they  are 
always  nearly  parallel,  they  hardly  ever  are  exactly  so. 
When  we  look  at  an  object,  the  axes  of  the  eyes  meet 
in  that  object :  and,  therefore,  make  an  angle,  which  is 
always  small,  but  will  be  greater  or  less,  according  as 
the  object  is  nearer  or  more  remote.  Nature  hath  very 
wisely  left  us  the  power  of  varying  the  parallelism  of 
our  eyes  a  little,  so  that  we  can  direct  them  to  the  same 
point,  whether  remote  or  near.  This,  no  doubt,  is 
learned  by  custom  :  and  accordingly  we  see,  that  it  is 
a  long  time  before  children  get  this  habit  in  perfection. 

This  power  of  varying  the  parallelism  of  the  eyes  is 
naturally  no  more  than  is  sufficient  for  the  purpose  in- 
tended by  it ;  but  by  much  practice  and  straining,  it  may 
be  increased.  Accordingly,  we  see,  that  some  have  ac- 
quired the  power  of  distorting  their  eyes  into  unnatural 
directions,  as  others  have  acquired  the  power  of  distort- 
ing their  bodies  into  unnatural  postures. 

Those  who  have  lost  the  sight  of  an  eye,  commonly 
lose  what  they  had  got  by  custom,  in  the  direction  of 
their  eyes,  but  retain  what  they  had  by  nature  ;  that  is, 
although  their  eyes  turn  and  move  always  together,  yet, 
when  they  look  upon  an  object,  the  blind  eye  will  often 
have  a  very  small  deviation  from  it ;  which  is  not  per- 
ceived by  a  slight  observer,  but  may  be  discerned  by  one 
accustomed  to  make  exact  observations  in  these  matters. 


SEC.  XI.]  THE  PHILOSOPHY  OF  REID.  215 

Section  XL 

OF   OUR   SEEING   OBJECTS  ERECT   BY   INVERTED   IMAGES. 

Another  phenomenon  which  hath  perplexed  philoso- 
phers, is  our  seeing  objects  erect,  when  it  is  well  known 
that  their  images  or  pictures  upon  the  tunica  retina  of  the 
eye  are  inverted. 

The  sagacious  Kepler  first  made  the  noble  discovery, 
that  distinct  but  inverted  pictures  of  visible  objects  are 
formed  upon  the  retina  by  the  rays  of  light  coming 
from  the  object.  The  same  great  philosopher  demon- 
strated, from  the  principles  of  optics,  how  these  pictures 
are  formed — to  wit,  That  the  rays  coming  from  any  one 
point  of  the  object,  and  falling  upon  the  various  parts  of 
the  pupil,  are,  by  the  cornea  and  crystalline,  refracted 
so  as  to  meet  again  in  one  point  of  the  retina,  and  there 
paint  the  colour  of  that  point  of  the  object  from  which 
they  come.  As  the  rays  from  different  points  of  the  ob- 
ject cross  each  other  before  they  come  to  the  retina,  the 
picture  they  form  must  be  inverted;  the  upper  part  of  the 
object  being  painted  upon  the  lower  part  of  the  retina, 
the  right  side  of  the  object  upon  the  left  of  the  retina,  and 
so  of  the  other  parts. 

This  philosopher  thought  chat  we  see  objects  erect  by 
means  of  these  inverted  pictures,  for  this  reason,  that, 
as  the  rays  from  different  points  of  the  object  cross  each 
other  before  they  fall  upon  the  retina,  we  conclude  that 
the  impulse  which  we  feel  upon  the  lower  part  of  the 
retina  comes  from  above,  and  that  the  impulse  which  we 
feel  upon  the  higher  part  comes  from  below. 

Des  Cartes  afterwards  gave  the  same  solution  of  this 
phenomenon,  and  illustrated  it  by  the  judgment  which 
we  form  of  the  position  of  objects  which  we  feel  with  our 
arms  crossed,  or  with  two  sticks  that  cross  each  other. 

But  we  cannot  acquiesce  in  this  solution.     First,   Be- 


2l6  THE  PHILOSOPHY   OF  REID.  [Cn.  VI. 

cause  it  supposes  our  seeing  things  erect,  to  be  a  deduc- 
tion of  reason,  drawn  from  certain  premises:  whereas  it 
seems  to  be  an  immediate  perception.  And,  secondly, 
Because  the  premises  from  which  all  mankind  are  sup- 
posed to  draw  this  conclusion,  never  entered  into  the 
minds  of  the  far  greater  part,  but  are  absolutely  un- 
known to  them.  We  have  no  feeling  or  perception  of 
the  pictures  upon  the  retina,  and  as  little  surely  of  the 
position  of  them.  In  order  to  see  objects  erect,  accord- 
ing to  the  principles  of  Kepler  or  Des  Cartes,  we  must 
previously  know  that  the  rays  of  light  come  from  the  ob- 
ject to  the  eye  in  straight  lines;  we  must  know  that  the 
rays  from  different  points  of  the  object  cross  one  another 
before  they  form  the  pictures  upon  the  retina;  and,  lastly, 
we  must  know  that  these  pictures  are  really  inverted. 
Now,  although  all  these  things  are  true,  and  known  to 
philosophers,  yet  they  are  absolutely  unknown  to  the  far 
greatest  part  of  mankind:  nor  is  it  possible  that  they  who 
are  absolutely  ignorant  of  them,  should  reason  from 
them,  and  build  conclusions  upon  them.  Since,  there- 
fore, visible  objects  appear  erect  to  the  ignorant  as  well 
as  to  the  learned,  this  cannot  be  a  conclusion  drawn  from 
premises  which  never  entered  into  the  minds  of  the  ig- 
norant. We  have  indeed  had  occasion  to  observe  many 
instances  of  conclusions  drawn,  either  by  means  of 
original  principles,  or  by  habit,  from  premises  which 
pass  through  the  mind  very  quickly,  and  which  are 
never  made  the  objects  of  reflection;  but  surely  no  man 
will  conceive  it  possible  to  draw  conclusions  from  prem- 
ises which  never  entered  into  the  mind  at  all. 

Bishop  Berkeley  having  justly  rejected 'this  solution, 
gives  one  founded  upon  his  own  principles;  wherein  he 
is  followed  by  the  judicious  Dr.  Smith,  in  his  "Optics;  " 
and  this  we  shall  next  explain  and  examine. 

That  ingenious  writer  conceives  the  ideas  of  sight  to 
be  altogether  unlike  those  of  touch.  And,  since  the 
notions  we  have  of  an  object  by  these  different  senses 


SEC.  XI.]  THE  PHILOSOPHY  OF  REID.  2I/ 

have  no  similitude,  we  can  learn  only  by  experience  how 
one  sense  will  be  affected,  by  what,  in  a  certain  manner, 
affects  the  other.  Figure,  position,  and  even  number, 
in  tangible  objects,  are  ideas  of  touch;  and,  although 
there  is  no  similitude  between  these  and  the  ideas  of 
sight,  yet  we  learn  by  experience,  that  a  triangle  affects 
the  sight  in  such  a  manner,  and  that  a  square  affects  it 
in  such  another  manner — hence  we  judge  that  which  af- 
fects it  in  the  first  manner,  to  be  a  triangle,  and  that 
which  affects  it  in  the  second,  to  be  a  square.  In  the 
same  way,  finding,  from  experience,  that  an  object  in  an 
erect  position  affects  the  eye  in  one  manner,  and  the 
same  object  in  an  inverted  position  affects  it  in  another, 
we  learn  to  judge,  by  the  manner  in  which  the  eye  is 
affected,  whether  the  object  is  erect  or  inverted.  In  a 
word,  visible  ideas,  according  to  this  author,  are  signs  of 
the  tangible;  and  the  mind  passeth  from  the  sign  to  the 
thing  signified,  not  by  means  of  any  similitude  between 
the  one  and  the  other,  nor  by  any  natural  principle,  but 
by  having  found  them  constantly  conjoined  in  experi- 
ence,- as  the  sounds  of  a  language  are  with  the  things 
they  signify:  so  that,  if  the  images  upon  the  retina  had 
been  always  erect,  they  would  have  shewn  the  objects 
erect,  in  the  manner  as  they  do  now  that  they  are  in- 
verted— nay,  if  the  visible  idea  which  we  now  have  from 
an  inverted  object,  had  been  associated  from  the  begin- 
ning with  the  erect  position  of  that  object,  it  would 
have  signified  an  erect  position,  as  readily  as  it  now  sig- 
nifies an  inverted  one.  And,  if  the  visible  appearance 
of  two  shillings  had  been  found  connected  from  the  be- 
ginning with  the  tangible  idea  of  one  shilling,  that 
appearance  would  as  naturally  and  readily  have  sig- 
nified the  unity  of  the  object  as  now  it  signifies  its 
duplicity. 

This  opinion  is,  undoubtedly,  very  ingenious  :  and, 
if  it  is  just,  serves  to  resolve  not  only  the  phaenomenon 
now  under  consideration,  but  likewise  that  which  we 


2l8  THE  PHILOSOPHY  OF  REID,  |CH.  VI. 

shall  next  consider — our  seeing  objects  single  with  two 
eyes. 

It  is  evident  that,  in  this  solution,  it  is  supposed  that 
we  do  not  originally,  and  previous  to  acquired  habits, 
see  things  either  erect  or  inverted,  of  one  figure  or 
another,  single  or  double  ;  but  learn,  from  experience, 
to  judge  of  their  tangible  position,  figure,  and  number, 
by  certain  visible  signs. 

Indeed,  it  must  be  acknowledged  to  be  extremely  diffi- 
cult to  distinguish  the  immediate  and  natural  objects  of 
sight,  from  the  conclusions  which  we  have  been  accus- 
tomed from  infancy  to  draw  from  them.  Bishop  Berkeley 
was  the  first  that  attempted  to  distinguish  the  one  from 
the  other,  and  to  trace  out  the  boundary  that  divides 
them.  And  if,  in  doing  so,  he  hath  gone  a  little  to  the 
right  hand  or  to  the  left,  this  might  be  expected  in  a  sub- 
ject altogether  new,  and  of  the  greatest  subtilty.  The 
nature  of  vision  hath  received  great  light  from  this  dis- 
tinction ;  and  many  phaenomena  in  optics,  which  before 
appeared  altogether  unaccountable,  have  been  clearly  and 
distinctly  resolved  by  it.  It  is  natural,  and  almost-  un- 
avoidable, to  one  who  hath  made  an  important  discovery 
in  philosophy,  to  carry  it  a  little  beyond  its  sphere,  and 
to  apply  it  to  the  resolution  of  phaenomena  which  do 
not  fall  within  its  province.  Even  the  great  Newton, 
when  he  had  discovered  the  universal  law  of  gravitation, 
and  observed  how  many  of  the  phaenomena  of  nature 
depend  upon  this,  and  other  laws  of  attraction  and  re- 
pulsion, could  not  help  expressing  his  conjecture,  that 
all  the  phaenomena  of  the  material  world  depend  upon 
attracting  and  repelling  forces  in  the  particles  of  matter. 
And  I  suspect  that  the  ingenious  Bishop  of  Cloyne,  having 
found  so  many  phaenomena  of  vision  reducible  to  the  con- 
stant association  of  the  ideas  of  sight  and  touch,  carried 
this  principle  a  little  beyond  its  just  limits. 

In  order  to  judge  as  well  as  we  can  whether  it  is  so, 
let  r.s  suppose  such  a   blind  man  as  Dr.   Saunderson, 


SEC.  XL]  THE  PHILOSOPHY  OF  REID.  £19 

having  all  the  knowledge  and  abilities  which  a  blind 
man  may  have,  suddenly  made  to  see  perfectly.  Let  us 
suppose  him  kept  from  all  opportunities  of  associating 
his  ideas  of  sight  with  those  of  touch,  until  the  former 
become  a  little  familiar;  and  the  first  surprise,  occa- 
sioned by  objects  so  new,  being  abated,  he  has  time  to 
canvass  them,  and  to  compare  them,  in  his  mind,  with 
the  notions  which  he  formerly  had  by  touch;  and,  in 
particular,  to  compare,  in  his  mind,  that  visible  exten- 
sion which  his  eyes  present,  with  the  extension  in  length 
and  breadth  with  which  he  was  before  acquainted. 

We  have  endeavoured  to  prove,  that  a  blind  man  may 
form  a  notion  of  the  visible  extension  and  figure  of  bod- 
ies, from  the  relation  which  it  bears  to  their  tangible 
extension  and  figure.  Much  more,  when  this  visible 
extension  and  figure  are  presented  to  his  eye,  will  he  be 
able  to  compare  them  with  tangible  extension  and  figure, 
and  to  perceive  that  the  one  has  length  and  breadth  as 
well  as  the  other;  that  the  one  may  be  bounded  by  lines, 
either  straight  or  curve,  as  well  as  the  other.  And, 
therefore,  he  will  perceive  that  there  may  be  visible  as 
well  as  tangible  circles,  triangles,  quadrilateral  and  mul- 
tilateral figures.  And,  although  the  visible  figure  is 
jcoloured,  and  the  tangible  is  not,  they  may,  notwith- 
standing, have  the  same  figure;  as  two  objects  of  touch 
may  have  the  same  figure,  although  one  is  hot  and  the 
other  cold. 

We  have  demonstrated,  that  the  properties  of  visible 
figure  differ  from  those  of  the  plain  figures  which  they 
represent;  but  it  was  observed,  at  the  same  time,  that 
when  the  object  is  so  small  as  to  be  seen  distinctly  at 
one  view,  and  is  placed  directly  before  the  eye,  the  dif- 
ference between  the  visible  and  the  tangible  figure  is  too 
small  to  be  perceived  by  the  senses  Thus,  it  is  true, 
that,  of  every  visible  triangle,  the  three  angles  are  greater 
than  two  right  angles;  whereas,  in  a  plain  triangle,  the 
three  angles  are  equal  to  two  right  angles;  but  when  the 


220  THE  PHILOSOPHY  OF  REID.  [CH.  VI. 

visible  triangle  is  small,  its  three  angles  will  be  so  nearly 
equal  to  two  right  angles,  that  the  sense  cannot  discern 
the  difference.  In  like  manner,  the  circumferences  of 
unequal  visible  circles  are  not,  but  those  of  plain  circles 
are,  in  the  ratio  of  their  diameters;  yet,  in  small  visible 
circles,  the  circumferences  are  very  nearly  in  the  ratio  of 
their  diameters;  and  the  diameter  bears  the  same  ratio  to 
the  circumference  as  in  a  plain  circle,  very  nearly. 

Hence  it  appears,  that  small  visible  figures  (and  such 
only  can  be  seen  distinctly  at  one  view)  have  not  only  a 
resemblance  to  the  plain  tangible  figures  which  have  the 
same  name,  but  are  to  all  senses  the  same:  so  that  if 
Dr.  Saunderson  had  been  made  to  see,  and  had  atten- 
tively viewed  the  figures  of  the  first  book  of  Euclid,  he 
might,  by  thought  and  consideration,  without  touching 
them,  have  found  out  that  they  were  the  very  figures  he 
was  before  so  well  acquainted  with  by  touch. 

When  plain  figures  are  seen  obliquely,  their  visible 
figure  differs  more  from  the  tangible ;  and  the  representa- 
tion which  is  made  to  the  eye,  of  solid  figures,  is  still 
more  imperfect ;  because  visible  extension  hath  not  three, 
but  two  dimensions  only.  Yet,  as  it  cannot  be  said  that 
an  exact  picture  of  a  man  hath  no  resemblance  of  the 
man,  or  that  a  perspective  view  of  a  house  hath  no  resem- 
blance of  the  house,  so  it  cannot  be  said,  with  any  pro- 
priety, that  the  visible  figure  of  a  man  or  of  a  house'hath 
no  resemblance  of  the  objects  which  they  represent. 

Bishop  Berkeley  therefore  proceeds  upon  a  capital  mis- 
take, in  supposing  that  there  is  no  resemblance  betwixt 
the  extension,  figure,  and  position  which  we  see,  and 
that  which  we  perceive  by  touch. 

We  may  further  observe,  that  Bishop  Berkeley's  sys- 
tem, with  regard  to  material  things,  must  have  made  him 
see  this  question,  of  the  erect  appearance  of  objects,  in 
a  very  different  light  from  that  in  which  it  appears  to 
those  who  do  not  adopt  his  system. 

In  his  theory  of  vision,  he  seems  indeed  to  allow,  that 


SEC.  XI.]  THE  PHILOSOPHY  OF  REID.  221 

there  is  an  external  material  world:  but  he  believed  that 
this  external  world  is  tangible  only,  and  not  visible  ;  and 
that  the  visible  world,  the  proper  object  of  sight,  is  not  ex- 
ternal, but  in  the  mind.  If  this  is  supposed,  he  that 
affirms  that  he  sees  things  erect  and  not  inverted,  affirms 
that  there  is  a  top  and  a  bottom,  a  right  and  a  left  in  the 
mind.  Now,  I  confess  I  am  not  so  well  acquainted  with 
the  topography  of  the  mind,  as  to  be  able  to  affix  a 
meaning  to  these  words  when  applied  to  it. 

We  shall  therefore  allow,  that,  if  visible  objects  were 
not  external,  but  existed  only  in  the  mind,  they  could 
have  no  figure,  or  position,  or  extension ;  and  that  it 
would  be  absurd  to  affirm,  that  they  are  seen  either  erect 
or  inverted,  or  that  there  is  any  resemblance  between 
them  and  the  objects  of  touch.  But  when  we  propose 
the  question,  why  objects  are  seen  erect  and  not  inverted, 
we  take  it  for  granted,  that  we  are  not  in  Bishop  Berke- 
ley's ideal  world,  but  in  that  world  which  men  who  yield 
to  the  dictates  of  common  sense,  believe  themselves  to 
inhabit.  We  take  it  for  granted,  that  the  objects  both 
of  sight  and  touch,  are  external,  and  have  a  certain  figure, 
and  a  certain  position  with  regard  to  one  another,  and 
with  regard  to  our  bodies,  whether  we  perceive  it  or  not. 

When  I  hold  my  walking-cane  upright  in  my  hand, 
and  look  at  it,  I  take  it  for  granted  that  I  see  and  handle 
the  same  individual  object.  When  I  say  that  I  feel  it 
erect,  my  meaning  is,  that  I  feel  the  head  directed  from 
the  horizon,  and  the  point  directed  towards  it ;  and  when 
I  say  that  I  see  it  erect,  I  mean  that  I  see  it  with  the  head 
directed  from  the  horizon,  and  the  point  towards  it.  I 
conceive  the  horizon  as  a  fixed  object  both  of  sight  and 
touch,  with  relation  to  which,  objects  are  said  to  be  high 
or  low,  erect  or  inverted;  and  when  the  question  is 
asked,  why  I  see  the  object  erect,  and  not  inverted,  it  is 
the  same  as  if  you  should  ask,  why  I  see  it  in  that  posi- 
tion which  it  really  hath,  or  why  the  eye  shews  the  real 
position  of  objects,  and  doth  not  shew  them  in  an  in- 


222  ±HE  PHILOSOPHY  OF  RElD.  tCH.  Vl. 

verted  position,  as  they  are  seen  by  a  common  astronom- 
ical telescope,  or  as  their  pictures  are  seen  upon  the 
retina  of  an  eye  when  it  is  dissected. 


Section  XII. 

THE   SAME   SUBJECT   CONTINUED. 

It  is  impossible  to  give  a  satisfactory  answer  to  this 
question,  otherwise  than  by  pointing  out  the  laws  of 
nature  which  take  place  in  vision  ;  for  by  these  the  phae- 
nomena  of  vision  must  be  regulated. 

Therefore,  I  answer,  First,  That,  by  a  law  of  nature, 
the  rays  of  light  proceed  from  every  point  of  the  object 
to  the  pupil  of  the  eye,  in  straight  lines  ;  Secondly,  That, 
by  the  laws  of  nature,  the  rays  coming  from  any  one 
point  of  the  object  to  the  various  parts  of  the  pupil,  are 
so  refracted  as  to  meet  again  in  one  point  of  the  retina  ; 
and  the  rays  from  different  points  of  the  object,  first 
crossing  each  other,  and  then  proceeding  to  as  many 
different  points  of  the  retina,  form  an  inverted  picture  of 
the  object. 

So  far  the  principles  of  optics  carry  us ;  and  experience 
further  assures  us,  that,  if  there  is  no  such  picture  upon 
the  retina,  there  is  no  vision  ;  and  that  such  as  the  picture 
on  the  retina  is,  such  is  the  appearance  of  the  object,  in 
colour  and  figure,  distinctness  or  indistinctness,  bright- 
ness or  faintness. 

It  is  evident,  therefore,  that  the  pictures  upon  the  ret- 
ina are,  by  the  laws  of  nature,  a  mean  of  vision;  but  in 
what  way  they  accomplish  their  end,  we  are  totally 
ignorant.  Philosophers  conceive,  that  the  impression 
made  on  the  retina  by  the  rays  of  light,  is  communicated 
to  the  optic  nerve,  and  by  the  optic  nerve  conveyed  to 
some  part  of  the  brain,  by  them  called  the  sensorium; 
and  that  the  impression  thus  conveyed  to  the  sensorium 


SEC.  XII.]  THE  PHILOSOPHY  OF  REID.  12$ 

is  immediately  perceived  by  the  mind,  which  is  supposed 
to  reside  there.  But  we  know  nothing  of  the  seat  of  the 
soul:  and  we  are  so  far  from  perceiving  immediately 
what  is  transacted  in  the  brain,  that  of  all  parts  of  the 
human  body  we  know  least  about  it.  It  is  indeed  very 
probable,  that  the  optic  nerve  is  an  instrument  of  vision 
no  less  necessary  than  the  retina;  and  that  some  impres- 
sion is  made  upon  it,  by  means  of  the  pictures  on  the 
retina.  But  of  what  kind  this  impression  is,  we  know 
nothing. 

There  is  not  the  least  probability  that  there  is  any 
picture  or  image  of  the  object  either  in  the  optic  nerve 
or  brain.  The  pictures  on  the  retina  are  formed  by  the 
rays  of  light;  and,  whether  we  suppose,  with  some,  that 
their  impulse  upon  the  retina  causes  some  vibration  of 
the  fibres  of  the  optic  nerve,  or,  with  others,  that  it  gives 
motion  to  some  subtile  fluid  contained  in  the  nerve, 
neither  that  vibration  nor  this  motion  can  resemble  the 
visible  object  which  is  presented  to  the  mind.  Nor  is 
there  any  probability  that  the  mind  perceives  the  pictures 
upon  the  retina.  These  pictures  are  no  more  objects  of 
our  perception,  than  the  brain  is,  or  the  optic  nerve. 
No  man  ever  saw  the  pictures  in  his  own  eye,  nor  in- 
deed the  pictures  in  the  eye  of  another,  until  it  was 
taken  out  of  the  head  and  duly  prepared. 

It  is  very  strange,  that  philosophers,  of  all  ages,  should  ] 
have  agreed  in  this  notion,  that  the  images  of  external 
objects  are  conveyed  by  the  organs  of  sense  to  the  brain, 
and  are  there  perceived  by  the  mind.  Nothing  can  be 
more  unphilosophical.  For,  First,  This  notion  hath  no 
foundation  in  fact  and  observation.  Of  all  the  organs  of 
sense,  the  eye  only,  as  far  as  we  can  discover,  forms  any 
kind  of  image  of  its  object;  and  the  images  formed  by 
the  eye  are  not  in  the  brain,  but  only  in  the  bottom  of 
the  eye;  nor  are  they  at  all  perceived  or  felt  by  the  mind. 
Secondly,  It  is  as  difficult  to  conceive  how  the  mind 
perceives  images  in  the  brain,  as  how  it  perceives  things 


±24  THE  PHILOSOPHY  OF  REID.  [CH.  VI. 

more  distant.  If  any  man  will  shew  how  the  mind  may 
perceive  images  in  the  brain,  I  will  undertake  to  shew 
how  it  may  perceive  the  most  distant  objects;  for,  if  we 
give  eyes  to  the  mind,  to  perceive  what  is  transacted  at 
home  in  its  dark  chamber,  why  may  we  not  make  these 
eyes  a  little  longer-sighted  ?  and  then  we  shall  have  no 
occasion  for  that  unphilosophical  fiction  of  images  in  the 
brain.  In  a  word,  the  manner  and  mechanism  of  the 
mind's  perception  is  quite  beyond  our  comprehension; 
and  this  way  of  explaining  it,  by  images  in  the  brain, 
seems  to  be  founded  upon  very  gross  notions  of  the 
mind  and  its  operations;  as  if  the  supposed  images  in 
the  brain,  by  a  kind  of  contact,  formed  similar  impres- 
sions or  images  of  objects  upon  the  mind,  of  which  im- 
pressions it  is  supposed  to  be  conscious, 

We  have  endeavoured  to  shew,  throughout  the  course 
of  this  inquiry,  that  the  impressions  made  upon  the  mind 
by  means  of  the  five  senses,  have  not  the  least  resem- 
blance to  the  objects  of  sense;  and,  therefore,  as  we  see 
no  shadow  of  evidence  that  there  are  any  such  images  in 
the  brain,  so  we  see  no  purpose,  in  philosophy,  that  the 
supposition  of  them  can  answer.  Since  the  picture  upon 
the  retina,  therefore,  is  neither  itself  seen  by  the  mind, 
nor  produces  any  impression  upon  the  brain  or  sensorium, 
which  is  seen  by  the  mind,  nor  makes  any  impression 
upon  the  mind  that  resembles  the  object,  it  may  still  be 
asked,  How  this  picture  upon  the  retina  causes  vision  ? 

Before  we  answer  this  question,  it  is  proper  to  observe, 
that,  in  the  operations  of  the  mind,  as  well  as  in  those  of 
bodies,  we  must  often  be  satisfied  with  knowing  that  cer- 
tain things  are  connected,  and  invariably  follow  one 
another,  without  being  able  to  discover  the  chain  that 
goes  between  them.  It  is  to  such  connections  that  we 
give  the  name  of  laws  of  nature-,  and  when  we  say  that 
one  thing  produces  another  by  a  law  of  nature,  this  sig- 
nifies no  more,  but  that  one  thing,  which  we  call  in 
popular  language  the  cause,  is  constantly  and  invariably 


SEC.  XII.]  THE  PHILOSOPHY   OF  REID.  225 

followed  by  another,  which  we  call  the  effect;  and  that 
we  know  not  how  they  are  connected.  Thus,  we  see  it 
is  a  fact,  that  bodies  gravitate  towards  bodies;  and  that 
this  gravitation  is  regulated  by  certain  mathematical  pro- 
portions, according  to  the  distances  of  the  bodies  from 
each  other,  and  their  quantities  of  matter.  Being  un- 
able to  discover  the  cause  of  this  gravitation,  and  pre- 
suming that  it  is  the  immediate  operation,  either  of  the 
Author  of  nature,  or  of  some  subordinate  cause,  which 
we  have  not  hitherto  been  able  to  reach,  we  call  it  a  law 
of  nature.  If  any  philosopher  should  hereafter  be  so 
happy,  as  to  discover  the  cause  of  gravitation,  this  can 
only  be  done  by  discovering  some  more  general  law  of 
nature,  of  which  the  gravitation  of  bodies  is  a  necessary 
consequence.  In  every  chain  of  natural  causes,  the 
highest  link  is  a  primary  law  of  nature,  and  the  highest 
link  which  we  can  trace,  by  just  induction,  is  either  this 
primary  law  of  nature,  or  a  necessary  consequence  of  it. 
To  trace  out  the  laws  of  nature,  by  induction  from  the 
phenomena  of  nature,  is  all  that  true  philosophy  aims  at, 
and  all  that  it  can  ever  reach. 

There  are  laws  of  nature  by  which  the  operations  of  the 
mind  are  regulated,  there  are  also  laws  of  nature  that 
govern  the  material  system  ;  and,  as  the  latter  are  the  ulti- 
mate conclusions  which  the  human  faculties  can  reach  in 
the  philosophy  of  bodies,  so  the  former  are  the  ultimate 
conclusions  we  can  reach  in  the  philosophy  of  minds. 

To  return,  therefore,  to  the  question  above  proposed, 
we  may  see,  from  what  hath  been  just  now  observed,  that 
it  amounts  to  this — By  what  law  of  nature  is  a  picture 
upon  the  retina  the  mean  or  occasion  of  my  seeing  an  ex- 
ternal object  of  the  same  figure  and  colour  in  a  contrary 
position,  and  in  a  certain  direction  from  the  eye  ? 

It  will,  without  doubt,  be  allowed  that  I  see  the  whole 
object  in  the  same  manner  and  by  the  same  law  by  which 
I  see  any  one  point  of  it.  Now  I  know  it  to  be  a  fact, 
that,  in  direct  vision,  I  see  every  point  of  the  object  in  the 


226  THE  PHILOSOPHY   OF   REID.  [Cn.  VI. 

direction  of  the  right  line  that  passeth  from  the  centre  of 
the  eye  to  that  point  of  the  object.  And  I  know,  like- 
wise, from  optics,  that  the  ray  of  light  that  comes  to  the 
centre  of  my  eye,  passes  on  to  the  retina  in  the  same 
direction.  Hence,  it  appears  to  be  a  fact,  that  every  point 
of  the  object  is  seen  in  the  direction  of  a  right  line  passing 
from  the  picture  of  that  point,  on  the  retina,  through  the 
centre  of  the  eye.  As  this  is  a  fact  that  holds  universally 
and  invariably,  it  must  either  be  a  law  of  nature  or  the 
necessary  consequence  of  some  more  general  law  of 
nature;  and,  according  to  the  just  rules  of  philosophising, 
we  may  hold  it  for  a  law  of  nature,  until  some  more 
general  law  be  discovered,  whereof  it  is  a  necessary  con- 
sequence— which,  I  suspect,  can  never  be  done. 

Thus,  we  see  that  the  phaenomena  of  vision  lead  us  by 
the  hand  to  a  law  of  nature,  or  a  law  of  our  constitution, 
of  which  law,  our  seeing  objects  erect  by  inverted  images, 
is  a  necessary  consequence.  For  it  necessarily  follows, 
from  the  law  we  have  mentioned,  that  the  object  whose 
picture  is  lowest  on  the  retina  must  be  seen  in  the  highest 
direction  from  the  eye;  and  that  the  object  whose  picture 
is  on  the  right  of  the  retina  must  be  seen  on  the  left;  so 
that,  if  the  pictures  had  been  erect  in  the  retina,  we 
should  have  seen  the  object  inverted.  My  chief  intention 
in  handling  this  question,  was  to  point  out  this  law  of 
nature,  which,  as  it  is  a  part  of  the  constitution  of  the 
human  mind,  belongs  properly  to  the  subject  of  this 
inquiry.  For  this  reason,  I  shall  make  some  farther 
remarks  upon  it,  after  doing  justice  to  the  ingenious  Dr. 
Porterfield,  who  long  ago,  in  the  "  Medical  Essays,"  or, 
more  lately,  in  his  "Treatise  of  the  Eye,"  pointed  out, 
as  a  primary  law  of  our  nature,  That  a  visible  object  ap- 
pears in  the  direction  of  a  right  line  perpendicular  to  the 
retina  at  that  point  where  its  image  is  painted.  If  lines 
drawn  from  the  centre  of  the  eye  to  all  parts  of  the  retina 
be  perpendicular  to  it,  as  they  must  be  very  nearly,  this 
coincides  with  the  law  we  have  mentioned,  and  is  the 


SEC.  XII.]  THE  PHILOSOPHY  OF  REID.  227 

same  in  other  words.  In  order,  therefore,  that  we  may 
have  a  more  distinct  notion  of  this  law  of  our  constitution, 
we  may  observe — 

1.  That  we  can  give  no  reason  why  the  retina  is,  of  all 
parts  of  the  body,  the  only  one  on  which  pictures  made 
by  the  rays  of  light  cause  vision;  and,  therefore,  we  must 
resolve  this  solely  into  a  law  of  our  constitution.     We 
may  form   such  pictures  by  means  of  optical  glasses, 
upon  the  hand,  or  upon  *any  other  part  of  the  body;  but 
they  are  not  felt,  nor  do  they  produce  anything  like 
vision.     A  picture  upon  the  retina  is  as  little  felt  as  one 
upon  the  hand;  but  it  produces  vision,    for  no   other 
reason  that  we  know,  but  because  it  is  destined  by  the 
wisdom  of  nature  to  this  purpose.     The  vibrations  of  the 
air  strike  upon  the  eye,  the   palate,   and  the  olfactory 
membrane,  with  the  same  force   as  upon  the  membrani 
tympani  of  the  ear.     The  impression  they  make  upon  the 
last  produces  the  sensation  of  sound;  but  their  impres- 
sion upon  any  of  the  former  produces  no  sensation  at  all. 
This  may  be  extended  to  all  the  senses,  whereof  each 
hath   its  peculiar  laws,  according  to  which  the  impres- 
sions made  upon  the  organ  of  that  sense,  produce  sensa- 
tions or  perceptions  in  the  mind,  that  cannot  be  pro- 
duced by  impressions  made  upon  any  other  organ. 

2.  We  may  observe,  that  the  laws  of  perception,  by 
the  different  senses,  are  very  different,   not  only  in  re- 
spect of  the  nature  of  the  objects  perceived  by  them,  but 
likewise  in  respect  of  the  notices  they  give  us  of  the  dis- 
tance and  situation   of  the  object.     In  all  of  them  the 
object  is  conceived  *   to  be  external,  and  to  have  real 
existence,   independent  of  our  perception  :  but  in  one, 
the  distance,  figure,  and  situation  of  the  object,  are  all 

*  The  common  sense  of  mankind  assures  us  that  the  object  of 
sense,  is  not  merely  conceived  to  be  external,  but  perceived  in  its  ex- 
ternality;  that  we  know  the  Non-Ego,  not  merely  mediately,  by  a 
representation  in  the  Ego,  but  immediately,  as  existing  though  only 
as  existing  in  relation  to  our  organs. — H. 


228  THE  PHILOSOPHY   OF  REID.  [CH.  VI. 

presented  to  the  mind;  in  another,  the  figure  and  situa- 
tion, but  not  the  distance;  and  in  others,  neither  figure, 
situation,  nor  distance.  In  vain  do  we  attempt  to  ac- 
count for  these  varieties  in  the  manner  of  perception  by 
the  different  senses,  from  principles  of  anatomy  or  natural 
philosophy.  They  must  at  last  be  resolved  into  the  will 
of  our  Maker,  who  intended  that  our  powers  of  percep- 
tion should  have  certain  limits,  and  adapted  the  organs 
of  perception,  and  the  laws  of  nature  by  which  they 
operate,  to  his  wise  purposes. 

When  we  hear  an  unusual  sound,  the  sensation  indeed 
is  in  the  mind,  but  we  know  that  there  is  something  ex- 
ternal that  produced  this  sound.  At  the  same  time,  our 
hearing  does  not  inform  us  whether  the  sounding  body 
is  near  or  at  a  distance,  in  this  direction  or  that ;  and 
therefore  we  look  round  to  discover  it. 

If  any  new  phaenomenon  appears  in  the  heavens,  we 
see  exactly  its  colour,  its  apparent  place,  magnitude,  and 
figure;  but  we  see  not  its  distance.  It  may  be  in  the  at- 
mosphere, it  may  be  among  the  planets,  or  it  may  be  in 
the  sphere  of  the  fixed  stars,  for  anything  the  eye  can  de- 
termine. 

The  testimony  of  the  sense  of  touch  reaches  only  to 
objects  that  are  contiguous  to  the  organ,  but,  with  re- 
gard to  them,  is  more  precise  and  determinate.  When 
we  feel  a  body  with  our  hand,  we  know  the  figure,  dis- 
tance, and  position  of  it,  as  well  as  whether  it  is  rough 
or  smooth,  hard  or  soft,  hot  or  cold. 

The  sensations  of  touch,  of  seeing,  and  hearing,  are 
all  in  the  mind,  and  can  have  no  existence  but  when 
they  are  perceived.  How  do  they  all  constantly  and  in- 
variably suggest  the  conception  and  belief  of  external 
objects,  which  exist  whether  they  are  perceived  or  not  ? 
No  philosopher  can  give  any  other  answer  to  this,  but 
that  such  is  the  constitution  of  our  nature.  How  do  we 
know  that  the  object  of  touch  is  at  the  finger's  end,  and 
nowhere  else  ? — that  the  object  of  sight  is  in  such  a  di- 


SEC.  XII.]  THE  PHILOSOPHY  OF  REID.  229 

rection  from  the  eye,  and  in  no  other,  but  maybe  at  any 
distance  ? — and  that  the  object  of  hearing  may  be  at  any 
distance,  and  in  any  direction  ?  Not  by  custom  surely 
— not  by  reasoning,  or  comparing  ideas — but  by  the 
constitution  of  our  nature.  How  do  we  perceive  visible 
objects  in  the  direction  of  right  lines  perpendicular  to 
that  part  of  the  retina  on  which  the  rays  strike,  while  we 
do  not  perceive  the  objects  of  hearing  in  lines  perpendic- 
ular to  the  membrana  tympani  upon  which  the  vibrations 
of  the  air  strike  ?  Because  such  are  the  laws  of  our  na- 
ture. How  do  we  know  the  parts  of  our  bodies  affected 
by  particular  pains  ?  Not  by  experience  or  by  reason- 
ing, but  by  the  constitution  of  nature.  The  sensation  of 
pain  is,  no  doubt,  in  the  mind,  and  cannot  be  said  to 
have  any  relation,  from  its  own  nature,  to  any  part  of 
the  body;  but  this  sensation,  by  our  constitution,  gives  a 
perception  of  some  particular  part  of  the  body,  whose 
disorder  causes  the  uneasy  sensation.  If  it  were  not  so, 
a  man  who  never  before  felt  either  the  gout  or  the  tooth- 
ache, when  he  is  first  seized  with  the  gout  in  his  toe, 
might  mistake  it  for  the  toothache. 

Every  sense,  therefore,  hath  its  peculiar  laws  and 
limits,  by  the  constitution  of  our  nature;  and  one  of  the 
laws  of  sight  is,  that  we  always  see  an  object  in  the  di- 
rection of  a  right  line,  passing  from  its  image  on  the  ret- 
ina through  the  centre  of  the  eye. 

3.  Perhaps  some  readers  will  imagine  that  it  is  easier, 
and  will  answer  the  purpose  as  well,  to  conceive  a  law 
of  nature,  by  which  we  shall  always  see  objects  in  the 
place  in  which  they  are,  and  in  their  true  position,  with- 
out having  recourse  to  images  on  the  retina,  or  to  the 
optical  centre  of  the  eye. 

To  this  I  answer,  that  nothing  can  be  a  law  of  nature 
which  is  contrary  to  fact.  The  law.s  of  nature  are  the 
most  general  facts  we  can  discover  in  the  operations  of 
nature.  Like  other  facts,  they  are  not  to  be  hit  upon  by 
a  happy  conjecture,  but  justly  deduced  from  observation; 


230  THE  PHILOSOPHY   OF   REID.  [Cn.  VI. 

like  other  general  facts,  they  are  not  to  be  drawn  from  a 
few  particulars,  but  from  a  copious,  patient,  and  cautious 
induction.  That  we  see  things  always  in  their  true 
place  and  position,  is  not  fact;  and  therefore  it  can  be 
no  law  of  nature.  In  a  plain  mirror,  I  see  myself,  and 
other  things,  in  places  very  different  from  those  they 
really  occupy.  And  so  it  happens  in  every  instance 
wherein  the  rays  coming  from  the  object  are  either  re- 
flected or  refracted  before  falling  upon  the  eye.  Those 
who  know  anything  of  optics,  know  that,  in  all  such 
cases,  the  object  is  seen  in  the  direction  of  a  line  passing 
from  the  centre  of  the  eye,  to  the  point  where  the  rays 
were  last  reflected  or  refracted;  and  that  upon  this  all  the 
powers  of  the  telescope  and  microscope  depend. 

Shall  we  say,  then,  that  it  is  a  law  of  nature,  that  the 
object  is  seen  in  the  direction  which  the  rays  have  when 
they  fall  on  the  eye,  or  rather  in  the  direction  contrary 
to  that  of  the  rays  when  they  fall  upon  the  eye  ?  No. 
This  is  not  true;  and  therefore  it  is  no  law  of  nature. 
For  the  rays,  from  any  one  point  of  the  object,  come  to 
all  parts  of  the  pupil;  and  therefore  must  have  different 
directions:  but  we  see  the  object  only  in  one  of  these  di- 
rections —to  wit,  in  the  direction  of  the  rays  that  come 
to  the  centre  of  the  eye.  And  this  holds  true,  even 
when  the  rays  that  should  pass  through  the  centre  are 
stopped,  and  the  object  is  seen  by  rays  that  pass  at  a  dis- 
tance from  the  centre. 

Perhaps  it  may  still  be  imagined,  that,  although  we 
are  not  made  so  as  to  see  objects  always  in  their  true 
place,  nor  so  as  to  see  them  precisely  in  the  direction  of 
the  rays  when  they  fall  upon  the  cornea;  yet  we  may  be 
so  made  as  to  see  the  object  in  the  direction  which  the 
rays  have  when  they  fall  upon  the  retina,  after  they  have 
undergone  all  their  refractions  in  the  eye — that  is,  in  the 
direction  in  which  the  rays  pass  from  the  crystalline  to 
the  retina.  But  neither  is  this  true ;  and  consequently  it 
is  no  law  of  our  constitution.  In  order  to  see  that  it  is 


SEC.  XII.]  THE  PHILOSOPHY  OF  REID.  231 

not  true,  we  must  conceive  all  the  rays  that  pass  from 
the  crystalline  to  one  point  of  the  retina,  as  forming  a 
small  cone,  whose  base  is  upon  the  back  of  the  crystal- 
line, and  whose  vertex  is  a  point  of  the  retina.  It  is  evi- 
dent that  the  rays  which  form  the  picture  in  this  point, 
have  various  directions,  even  after  they  pass  the  crystal- 
line: yet  the  object  is  seen  only  in  one  of  these  directions 
— to  wit,  in  the  direction  of  the  rays  that  come  from  the 
centre  of  the  eye.  Nor  is  this  owing  to  any  particular 
virtue  in  the  central  rays,  or  in  the  centre  itself;  for  the 
central  rays  may  be  stopped.  When  they  are  stopped, 
the  image  will  be  formed  upon  the  same  point  of  the 
retina  as  before,  by  rays  that  are  not  central,  nor  have 
the  same  direction  which  the  central  rays  had:  and  in 
this  case  the  object  is  seen  in  the  same  direction  as  be- 
fore, although  there  are  now  no  rays  corning  in  that  di- 
rection. 

From  this  induction  we  conclude,  That  our  seeing  an 
object  in  that  particular  direction  in  which  we  do  see  it, 
is  not  owing  to  any  law  of  nature  by  which  we  are  made 
to  see  it  in  the  direction  of  the  rays,  either  before  their 
refractions  in  the  eye,  or  after,  but  to  a  law  of  our  na- 
ture, by  which  we  see  the  object  in  the  direction  of  the 
right  line  that  passeth  from  the  picture  of  the  object  upon 
the  retina  to  the  centre  of  the  eye. 

The  facts  upon  which  I  ground  this  induction,  are 
taken  from  some  curious  experiments  of  Scheiner,  in  his 
"Fundamentum  Opticum,"  quoted  by  Dr.  Porterfield, 
and  confirmed  by  his  experience.  I  have  also  repeated 
these  experiments,  and  found  them  to  answer.  As  they 
are  easily  made,  and  tend  to  illustrate  and  confirm  the 
law  of  nature  I  have  mentioned,  I  shall  recite  them  as 
briefly  and  distinctly  as  I  can. 

Experiment  i.  Let  a  very  small  object,  such  as  the 
head  of  a  pin,  well  illuminated,  be  fixed  at  such  a  dis- 
tance from  the  eye  as  to  be  beyond  the  nearest  limit  and 
within  the  farthest  limit  of  distinct  vision.  For  a  young 


232  THE  PHILOSOPHY  OF  REID.  [Cn.  VI. 

eye,  not  near-sighted,  the  object  may  be  placed  at  the 
distance  of  eighteen  inches.  Let  the  eye  be  kept  steadily 
in  one  place,  and  take  a  distinct  view  of  the  object. 
We  know,  from  the  principles  of  optics,  that  the  rays 
from  any  one  point  of  this  object,  whether  they  pass 
through  the  centre  of  the  eye,  or  at  any  distance  from 
the  centre  which  the  breadth  of  the  pupil  will  permit,  do 
all  unite  again  in  one  point  of  the  retina.  We  know, 
also,  that  these  rays  have  different  directions,  both  be- 
fore they  fall  upon  the  eye,  and  after  they  pass  through 
the  crystalline. 

Now,  we  can  see  the  object  by  any  one  small  parcel 
of  these  rays,  excluding  the  rest,  by  looking  through  a 
small  pin-hole  in  a  card.  Moving  this  pin-hole  over 
the  various  parts  of  the  pupil,  we  can  see  the  object, 
first  by  the  rays  that  pass  above  the  centre  of  the  eye, 
then  by  the  central  rays,  then  by  the  rays  that  pass 
below  the  centre,  and  in  like  manner  by  the  rays  that 
pass  on  the  right  and  left  of  the  centre.  Thus,  we  view 
this  object,  successively,  by  rays  that  are  central,  and  by 
rays  that  are  not  central ;  by  rays  that  have  different  di- 
rections, and  are  variously  inclined  to  each  other,  both 
when  they  fall  upon  the  cornea,  and  when  they  fall  upon 
the  retina;  but  always  by  rays  which  fall  upon  the  same 
point  of  the  retina.  And  what  is  the  event  ?  It  is  this — 
that  the  object  is  seen  in  the  same  individual  direction, 
whether  seen  by  all  these  rays  together,  or  by  any  one 
parcel  of  them. 

Experiment  2.  Let  the  object  above  mentioned  be 
now  placed  within  the  nearest  limit  of  distinct  vision — 
that  is,  for  an  eye  that  is  not  near-sighted,  at  the  dis- 
tance of  four  or  five  inches.  We  know  that,  in  this  case, 
the  rays  coming  from  one  point  of  the  object  do  not 
meet  in  one  point  of  the  retina,  but  spread  over  a  small 
circular  spot  of  it;  the  central  rays  occupying  the  centre 
of  this  circle,  the  rays  that  pass  above  the  centre  occupy- 
ing the  upper  part  of  the  circular  spot,  and  so  of  the  rest. 


SEC.  Xit.)  THE  PHILOSOPHY  OF  REID.  233 

And  we  know  that  the  object  is,  in  this  case,  seen  con- 
fused; every  point  of  it  being  seen,  not  in  one,  but  in  va- 
rious directions.  To  remedy  this  confusion,  we  look  at 
the  object  through  the  pin-hole,  and  while  we  move  the 
pin-hole  over  the  various  parts  of  the  pupil,  the  object 
does  not  keep  its  place,  but  seems  to  move  in  a  contrary 
direction. 

It  is  here  to  be  observed,  that,  when  the  pin-hole  is 
carried  upwards  over  the  pupil,  the  picture  of  the  object 
is  carried  upwards  upon  the  retina,  and  the  object,  at 
the  same  time,  seems  to  move  downwards,  so  as  to  be 
always  in  the  right  line,  passing  from  the  picture  through 
the  centre  of  the  eye.  It  is  likewise  to  be  observed,  that 
the  rays  which  form  the  upper  and  the  lower  pictures 
upon  the  retina  do  not  cross  each  other,  as  in  ordinary 
vision  ;  yet,  still,  the  higher  picture  shews  the  object 
lower,  and  the  lower  picture  shews  the  object  higher, 
in  the  same  manner  as  when  the  rays  cross  each  other. 
Whence  we  may  observe,  by  the  way,  that  this  phaenom- 
enon  of  our  seeing  objects  in  a  position  contrary  to  that 
of  their  pictures  upon  the  retina,  does  not  depend  upon 
the  crossing  of  the  rays,  as  Kepler  and  Des  Cartes  con- 
ceived. 

Experiment  3.  Other  things 'remaining  as  in  the  last 
experiment,  make  three  pin-holes  in  a  straight  line,  so 
near  that  the  rays  coming  from  the  object  through  all 
the  holes  may  enter  the  pupil  at  the  same  time.  In  this 
case,  we  have  a  very  curious  phaenomenon  ;  for  the  ob- 
ject is  seen  triple  with  one  eye.  And  if  you  make  more 
holes  within  the  breadth  of  the  pupil,  you  will  see  as 
many  objects  as  there  are  holes.  However,  we  shall  sup- 
pose them  only  three — one  on  the  right,  one  in  the  mid- 
dle and  one  on  the  left ;  in  which  case  you  see  three  ob- 
jects standing  in  a  line  from  right  to  left. 

It  is  here  to  be  observed,  that  there  are  three  pictures 
on  the  retina  ;  that  on  the  left  being  formed  by  the  rays 
which  pass  on  the  left  of  the  eye's  centre,  the  middle 


234  THE  PHILOSOPHY  OF  REID,  tCn.  VI. 

picture  being  formed  by  the  central  rays,  and  the  right- 
hand  picture  by  the  rays  which  pass  on  the  right  of  the 
eye's  centre.  It  is  farther  to  be  observed,  that  the  ob- 
ject which  appears  on  the  right,  is  not  that  which  is  seen 
through  the  hole  on  the  right,  but  that  which  is  seen 
through  the  hole  on  the  left ;  and,  in  like  manner,  the 
left-hand  object  is  seen  through  the  hole  on  the  right, 
as  is  easily  proved  by  covering  the  holes  successively  :  so 
that,  whatever  is  the  direction  of  the  rays  which  form  the 
right-hand  and  left-hand  pictures,  still  the  right-hand 
picture  shews  a  left-hand  object,  and  the  left-hand  pict- 
ure shews  a  right-hand  object. 

Experiment  4.  It  is  easy  to  see  how  the  two  last  ex- 
periments may  be  varied,  by  placing  the  object  beyond 
the  farthest  limit  of  distinct  vision.  In  order  to  make 
this  experiment,  I  looked  at  a  candle  at  the  distance  of 
ten  feet,  and  put  the  eye  of  my  spectacles  behind  the 
card,  that  the  rays  from  the  same  point  of  the  object 
might  meet  and  cross  each  other,  before  they  reached 
the  retina.  In  this  case,  as  in  the  former,  the  candle 
was  seen  triple  through  the  three  pin-holes  ;  but  the 
candle  on  the  right  was  seen  through  the  hole  on  the 
right ;  and,  on  the  contrary,  the  left-hand  candle  was 
seen  through  the  hole  on  the  left.  In  this  experiment  it 
is  evident,  from  the  principles  of  optics,  that  the  rays 
fcfrming  the  several  pictures  on  the  retina  cross  each 
other  a  little  before  they  reach  the  retina  ;  and,  therefore, 
the  left-hand  picture  is  formed  by  the  rays  which  pass 
through  the  hole  on  the  right  :  so  that  the  position  of 
the  pictures  is  contrary  to  that  of  the  holes  by  which 
they  are  formed  ;  and,  therefore,  is  also  contrary  to  that 
of  their  objects — as  we  have  found  it  to  be  in  the  former 
experiments. 

These  experiments  exhibit  several  uncommon  phae- 
nomena,  that  regard  the  apparent  place,  and  the  direc- 
tion of  visible  objects  from  the  eye  ;  phenomena  that 
seem  to  be  most  contrary  to  the  common  rules  of  vision. 


SEC.  XII.)  THE  PHILOSOPHY  OF  REID.  235 

When  we  look  at  the  same  time  through  three  holes  that 
are  in  a  right  line,  and  at  certain  distances  from  each 
other,  we  expect  that  the  objects  seen  through  them 
should  really  be,  and  should  appear  to  be,  at  a  distance 
from  each  other.  Yet,  by  the  first  experiment,  we  may, 
through  three  such  holes,  see  the  same  object,  and  the 
same  point  of  that  object ;  and  through  all  the  three  it 
appears  in  the  same  individual  place  and  direction. 

When  the  rays  of  light  come  from  the  object  in  right 
lines  to  the  eye,  without  any  reflection,  inflection,  or 
refraction,  we  expect  that  the  object  should  appear  in 
its  real  and  proper  direction  from  the  eye  ;  and  so  it 
commonly  does.  But  in  the  second,  third,  and  fourth 
experiments,  we  see  the  object  in  a  direction  which  is 
not  its  true  and  real  direction  from  the  eye,  although  the 
rays  come  from  the  object  to  the  eye,  without  any  in- 
flection, reflection,  or  refraction. 

When  both  the  object  and  the  eye  are  fixed  without 
the  least  motion,  and  the  medium  unchanged,  we  expect 
that  the  object  should  appear  to  rest,  and  keep  the  same 
place.  Yet,  in  the  second  and  fourth  experiments,  when 
both  the  eye  and  the  object  are  at  rest,  and  the  medium 
unchanged,  we  make  the  object  appear  to  move  upwards 
or  downwards,  or  in  any  direction  we  please. 

When  we  look,  at  the  same  time  and  with  the  same 
eye,  through  holes  that  stand  in  a  line  from  right  to  left, 
we  expect  that  the  object  seen  through  the  left-hand  hole 
should  appear  on  the  left,  and  the  object  seen  through 
the  right-hand  hole  should  appear  on  the  right.  Yet,  in 
the  third  experiment,  we  find  the  direct  contrary. 

Although  many  instances  occur  in  seeing  the  same  ob- 
ject double  with  two  eyes,  we  always  expect  that  it  should 
appear  single  when  seen  only  by  one  eye.  Yet,  in  the 
second  and  fourth  experiments,  we  have  instances 
wherein  the  same  object  may  appear  double,  triple,  or 
quadruple  to  one  eye,  without  the  help  of  a  polyhedron  or 
multiplying  glass. 


236  THE  PHILOSOPHY  OF  REID.  [CH.  VI. 

All  these  extraordinary  phenomena,  regarding  the  di- 
rection of  visible  objects  from  the  eye,  as  well  as  those 
that  are  common  and  ordinary,  lead  us  to  that  law  of 
nature  which  I  have  mentioned,  and  are  the  necessary 
consequences  of  it.  And,  as  there  is  no  probability  that 
we  shall  ever  be  able  to  give  a  reason  why  pictures  upon 
the  retina  make  us  see  external  objects,  any  more  than 
pictures  upon  the  hand  or  upon  the  cheek  ;  or,  that  we 
shall  ever  be  able  to  give  a  reason,  why  we  see  the  ob- 
ject in  the  direction  of  a  line  passing  from  its  picture 
through  the  centre  of  the  eye,  rather  than  in  any  other 
direction — I  am,  therefore,  apt  to  look  upon  this  law  as 
a  primary  law  of  our  constitution. 

To  prevent  being  misunderstood,  I  beg  the  reader  to 
observe,  that  I  do  not  mean  to  affirm  that  the  picture 
upon  the  retina  will  make  us  see  an  object  in  the  direc- 
tion mentioned,  or  in  any  direction,  unless  the  optic 
nerve,  and  the  other  more  immediate  instruments  of  vis- 
ion, be  sound,  and  perform  their  function.  We  know 
not  well  what  is  the  office  of  the  optic  nerve,  nor  in  what 
manner  it  performs  that  office ;  but  that  it  hath  some 
part  in  the  faculty  of  seeing,  seems  to  be  certain  ;  be- 
cause, in  an  amaurosis,  which  is  believed  to  be  a  dis- 
order of  the  optic  nerve,  the  pictures  on  the  retina  are 
clear  and  distinct,  and  yet  there  is  no  vision. 

We  know  still  less  of  the  use  and  function  of  the 
choroid  membrane  ;  but  it  seems  likewise  to  be  neces- 
sary to  vision  :  for  it  is  well  known,  that  pictures  upon 
that  part  of  the  retina  where  it  is  not  covered  by  the 
choroid — I  mean  at  the  entrance  of  the  optic  nerve — 
produce  no  vision  any  more  than  a  picture  upon  the 
hand.  We  acknowledge,  therefore,  that  the  retina  is  not 
the  last  and  most  immediate  instrument  of  the  mind  in 
vision.  There  are  other  material  organs,  whose  oper- 
ation is  necessary  to  seeing,  even  after  the  pictures  upon 
the  retina  are  formed.  If  ever  we  come  to  know  the 
structure  and  use  of  the  choroid  membrane,  the  optic 


SfiC.  XII.]  THE  PHILOSOPHV   OF   REID.  $37 

nerve,  and  the  brain,  and  what  impressions  are  made 
upon  them  by  means  of  the  pictures  on  the  retina, 
some  more  links  of  the  chain  may  be  brought  within  our 
view,  and  a  more  general  law  of  vision  discovered  ;  but, 
while  we  know  so  little  of  the  nature  and  office  of  these 
more  immediate  instruments  of  vision,  it  seems  to  be  im- 
possible to  trace  its  laws  beyond  the  pictures  upon  the 
retina. 

Neither  do  I  pretend  to  say,  that  there  may  not  be 
diseases  of  the  eye,  or  accidents,  which  may  occasion 
our  seeing  objects  in  a  direction  somewhat  different  from 
that  mentioned  above.  I  shall  beg  leave  to  mention  one 
instance  of  this  kind  that  concerns  myself. 

In  May,  1761,  being  occupied  in  making  an  exact 
meridian,  in  order  to  observe  the  transit  of  Venus,  I 
rashly  directed  to  the  sun,  by  my  right  eye,  the  cross 
hairs  of  a  small  telescope.  I  had  often  done  the  like  in 
my  younger  days  with  impunity  ;  but  I  suffered  by  it  at 
last,  which  I  mention  as  a  warning  to  others. 

I  soon  observed  a  remarkable  dimness  in  that  eye;  and 
for  many  weeks,  when  I  was  in  the  dark,  or  shut  my 
eyes,  there  appeared  before  the  right  eye  a  lucid  spot, 
which  trembled  much  like  the  image  of  the  sun  seen 
by  reflection  from  water.  This  appearance  grew  fainter, 
and  less  frequent,  by  degrees ;  so  that  now  there  are 
seldom  any  remains  of  it.  But  some  other  very  sensible 
effects  of  this  hurt  still  remain.  For,  First,  The  sight 
of  the  right  eye  continues  to  be  more  dim  than  that  of 
the  left.  Secondly,  The  nearest  limit  of  distinct  vision 
is  more  remote  in  the  right  eye  than  in  the  other ;  al- 
though, before  the  time  mentioned,  they  were  equal  in 
both  these  respects,  as  I  had  found  by  many  trials.  But, 
thirdly,  what  I  chiefly  intended  to  mention  is,  That  a 
straight  line,  in  some  circumstances,  appears  to  the  right 
eye  to  have  a  curvature  in  it.  Thus,  when  I  look  upon 
a  music  book,  and,  shutting  my  left  eye,  direct  the  right 
to  a  point  of  the  middle  line  of  the  five  which  compose 


238  THE  PHILOSOPHY  OF  REID.  [Cn.  VI. 

the  staff  of  music,  the  middle  line  appears  dim,  indeed, 
at  the  point  to  which  the  eye  is  directed,  but  straight;  at 
the  same  time,  the  two  lines  above  it,  and  the  two  below 
it,  appear  to  be  bent  outwards,  and  to  be  more  distant 
from  each  other  and  from  the  middle  line,  than  at  other 
parts  of  the  staff,  to  which  the  eye  is  not  directed. 
Fourthly,  Although  I  have  repeated  this  experiment 
times  innumerable,  within  these  sixteen  months,  I  do 
not  find  that  custom  and  experience  takes  away  this  ap- 
pearance of  curvature  in  straight  lines.  Lastly,  This  ap- 
pearance of  curvature  is  perceptible  when  I  look  with 
the  right  eye  only,  but  not  when  I  look  with  both  eyes; 
yet  I  see  better  with  both  eyes  together,  than  even  with 
the  left  eye  alone. 

I  have  related  this  fact  minutely  as  it  is,  without  re- 
gard to  any  hypothesis;  because  I  think  such  uncommon 
facts  deserve  to  be  recorded.  I  shall  leave  it  to  others 
to  conjecture  the  cause  of  this  appearance.  To  me  it 
seems  most  probable,  that  a  small  part  of  the  retina 
toward  the  centre  is  shrunk,  and  that  thereby  the  contig- 
uous parts  are  drawn  nearer  to  the  centre,  and  to  one  an- 
other, than  they  were  before;  and  that  objects  whose  im- 
ages fall  on  these  parts,  appear  at  that  distance  from  each 
other  which  corresponds,  not  to  the  interval  of  the  parts 
in  their  present  preternatural  contraction,  but  to  their  in- 
terval in  their  natural  and  sound  state. 


Section  XIII. 

OF   SEEING  OBJECTS  SINGLE   WITH   TWO   EYES. 

Another  phaenomenon  of  vision  which  deserves  atten- 
tion, is  our  seeing  objects  single  with  two  eyes.  There 
are  two  pictures  of  the  object,  one  on  each  retina,  and 
each  picture  by  itself  makes  us  see  an  object  in  a  certain 
direction  from  the  eye;  yet  both  together  commonly 


SEC.XIH.]  THE  PHILOSOPHY  OF  REID.  239 

make  us  see  only  one  object.  All  the  accounts  or  solu- 
tions of  this  phenomenon  given  by  anatomists  and  phi- 
losophers seem  to  be  unsatisfactory.  I  shall  pass  over 
the  opinions  of  Galen,  of  Gassendus,  of  Baptista  Porta, 
and  of  Rohault.  The  reader  may  see  these  examined 
and  refuted  by  Dr.  Porterfield.  I  shall  examine  Dr. 
Porterfield's  own  opinion,  Bishop  Berkeley's,  and  some 
others.  But  it  will  be  necessary  first  to  ascertain  the 
facts;  for,  if  we  mistake  the  phenomena  of  single  and 
double  vision,  it  is  ten  to  one  that  this  mistake  will  lead 
us  wrong  in  assigning  the  causes.  This  likewise  we 
ought  carefully  to  attend  to,  which  is  acknowledged  in 
theory  by  all  who  have  any  true  judgment  or  just  taste 
in  inquiries  of  this  nature,  but  is  very  often  overlooked 
in  practice — namely,  that,  in  the  solution  of  natural 
phaenomena,  all  the  length  that  the  human  faculties  can 
carry  us,  is  only  this,  that,  from  particular  phaenomena, 
we  may,  by  induction,  trace  out  general  phaenomena,  of  \ 
which  all  the  particular  ones  are  necessary  consequences.  . 
And  when  we  have  arrived  at  the  most  general  phenom- 
ena we  can  reach,  there  we  must  stop.  If  it  is  asked, 
Why  such  a  body  gravitates  towards  the  earth  ?  all  the 
answer  that  can  be  given  is,  Because  all  bodies  gravitate 
towards  the  earth.  This  is  resolving  a  particular  phae- 
nomenon  into  a  general  one.  If  it  should  again  be  asked, 
Why  do  all  bodies  gravitate  toward  the  earth  ?  we  can 
give  no  other  solution  of  this  phaenomenon,  but  that  all 
bodies  whatsoever  gravitate  towards  each  other.  This  is 
\resolving  a  general  phaenomenon  into  a  more  general 
one.  If  it  should  be  asked,  Why  all  bodies  gravitate  to 
one  another?  we  cannot  tell;  but,  if  we  could  tell,  it 
could  only  be  by  resolving  this  universal  gravitation  of 
bodies  into  some  other  phaenomenon  still  more  general, 
and  of  which  the  gravitation  of  all  bodies  is  a  particular 
instance.  The  most  general  phaenomena  we  can  reach, 
are  what  we  call  laws  of  nature;  so  that  the  laws  of  na- 
ture are  nothing  else  but  the  most  general  facts  relating 


240  THE  PHILOSOPHY  OF  REID.  [CH.  VI. 

to  the  operations  of  nature,  which  include  a  great  many 
particular  facts  under  them.  And  if,  in  any  case,  we 
should  give  the  name  of  a  law  of  nature  to  a  general 
phaenomenon,  which  human  industry  shall  afterwards 
trace  to  one  more  general,  there  is  no  great  harm  done. 
The  most  general  assumes  the  name  of  a  law  of  nature 
when  it  is  discovered,  and  the  less  general  is  contained 
and  comprehended  in  it.  Having  premised  these  things, 
we  proceed  to  consider  the  phenomena  of  single  and 
double  vision,  in  order  to  discover  some  general  princi- 
ple to  which  they  all  lead,  and  of  which  they  are  the 
necessary  consequences.  If  we  can  discover  any  such 
general  principle,  it  must  either  be  a  law  of  nature, 
or  the  necessary  consequence  of  some  law  of  nature; 
and  its  authority  will  be  equal  whether  it  is  the  first  or 
the  last. 

1.  We  find  that,  when  the  eyes  are  sound  and  perfect, 
and   the  axes   of  both  directed  to  one  point,  an  object 
placed  in  that  point  is  seen  single — and  here  we  observe, 
that  in  this  case  the  two  pictures  which  shew  4the  object 
single,  are  in  the  centres  of  the  retina.     When  two  pict- 
ures of  a  small  object  are  formed  upon   points  of  the 
retina,  if  they  shew  the  objects  single,  we  shall,  for  the 
sake  of  perspicuity,  call  such  two  points  of  the   retina, 
corresponding  points;  and  where  the  object  is  seen  double, 
we  shall  call  the  points  of  the  retina  on  which  the  pict- 
ures are  formed,  points  that  do  not  correspond.     Now,  in 
this  first  phsenomenon,  it  is  evident,  that  the  two  centres 
of  the  retina  are  corresponding  points. 

2.  Supposing  the  same  things  as  in  the  last  phenomenon, 
other  objects  at  the  same  distance  from  the  eyes  as  that  to 
which  their  axes  are  directed,  do  also  appear  single.   Thus, 
if  I  direct  my  eyes  to  a  candle  placed  at  the  distance  of 
ten  feet,  and,  while  I  look  at  this  candle,  another  stands  at 
the  same  distance  from  my  eyes,  within  the  field  of  vision, 
I  can,  while  I  look  at  the  first  candle,  attend  to  the  ap- 
pearance which  the  second  makes  to  the  eye;  and  I  find 


SEC.  XIII.)  THE  PHILOSOPHY   OF  REID.  241 

that  in  this  case  it  always  appears  single.  It  is  here 
to  be  observed,  that  the  pictures  of  the  second  candle 
do  not  fall  upon  the  centres  of  the  retince,  but  they 
both  fall  upon  the  same  side  of  the  centres — that  is, 
both  to  the  right,  or  both  to  the  left;  and  both  are 
at  the  same  distance  from  the  centres.  This  might 
easily  be  demonstrated  from  the  principles  of  optics. 
Hence  it  appears,  that  in  this  second  phenomenon 
of  single  vision,  the  corresponding  points  are  points  of 
the  two  retin-ce,  which  are  similarly  situate  with  respect 
to  the  two  centres,  being  both  upon  the  same  side  of  the 
centre,  and  at  the  same  distance  from  it.  It  appears 
likewise,  from  this  phenomenon,  that  every  point  in  one 
retina  corresponds  with  that  which  is  similarly  situate 
in  the  other. 

3.  Supposing  still  the  same  things,  objects  which   are 
much  nearer  to   the  eyes,  or  much  more  distant  from 
them,    than   that   to  which  the  two  eyes  are  directed, 
appear  double.     Thus,  if  the  candle  is  placed   at  the 
distance   of  ten   feet,  and   I   hold   my  finger  at  arms- 
length  between  my  eyes  and  the  candle — when  I  look  at 
the  candle,  I  see  my  finger  double;   and  when  I  look  at 
my  finger,  I  see  the  candle  double;  and  the  same  thing 
happens  with  regard  to  all  other  objects  at  like  distances 
which  fall  within  the  sphere  of  vision.     In  this  phsenom- 
enon,  it  is  evident  to  those  who  understand  the  princi- 
ples of  optics,  that  the  pictures  of  the  objects  which  are 
seen  double,  do  not  fall  upon  the  points  of  the  retince 
which  are  similarly  situate,  but  that  the  pictures  of  the 
objects  seen  single,  do  fall  upon  points  similarly  situate. 
Whence  we  infer,  that,  as  the  points  of  the  two  retina, 
which  are  similarly  situate  with  regard  to  the  centres,  do 
correspond,  so  those  which  are  dissimilarly  situate  do 
not  correspond. 

4.  It  is  to  be  observed,  that,  although,  in  such  cases 
as  are  mentioned  in  the  last  phaenomenon,  we  have  been 
accustomed  from  infancy  to  see  objects  double  which 


242  THE   PHILOSOPHY   OF   REID.  [€H.  VI. 

we  know  to  be  single;  yet  custom,  and  experience  of  the 
unity  of  the  object,  never  take  away  this  appearance  of 
duplicity. 

5.  It  may,  however,  be  remarked  that  the  custom  of 
attending  to  visible  appearances  has  a  considerable  ef- 
fect, and  makes  the  phenomenon  of  double  vision  to 
be  more  or  less  observed  and  remembered.  Thus  you 
may  find  a  man  that  can  say,  with  a  good  conscience,  that 
he  never  saw  things  double  all  his  life;  yet  this  very  man, 
put  in  the  situation  above  mentioned,  with  his  finger  be- 
tween him  and  the  candle,  and  desired  to  attend  to  the 
appearance  of  the  object  which  he  does  not  look  at,  will, 
upon  the  first  trial,  see  the  candle  double,  when  he  looks 
at  his  finger;  and  his  finger  double,  when  he  looks  at  the 
candle.  Does  he  now  see  otherwise  than  he  saw  before? 
No;  surely;  but  he  now  attends  to  what  he  never  attended 
to  before.  The  same  double  appearance  of  an  object 
hath  been  a  thousand  times  presented  to  his  eye  before 
now,  but  he  did  not  attend  to  it;  and  so  it  is  as  little  an 
object  of  his  reflection  and  memory,  as  if  it  had  never 
happened. 

When  we  look  at  an  object,  the  circumjacent  objects 
may  be  seen  at  the  same  time,  although  more  obscurely 
and  indistinctly:  for  the  eye  hath  a  considerable  field  of 
vision,  which  it  takes  in  at  once.  But  we  attend  only 
to  the  object  we  look  at.  The  other  objects  which  fall 
within  the  field  of  vision,  are  not  attended  to;  and  there- 
fore are  as  if  they  were  not  seen.  If  any  of  them  draws 
our  attention,  it  naturally  draws  the  eyes  at  the  same 
time  :  for,  in  the  common  course  of  life,  the  eyes  always 
follow  the  attention  :  or  if  at  any  time,  in  a  revery,  they 
are  separated  from  it,  we  hardly  at  that  time  see  what  is 
directly  before  us.  Hence  we  may  see  the  reason  why 
the  man  we  are  speaking  of  thinks  that  he  never  before 
saw  an  object  double.  When  he  looks  at  any  object,  he 
sees  it  single,  and  takes  no  notice  of  other  visible  objects 
at  that  time,  whether  they  appear  single  or  double.  If 


SEC.  XIII.]  THE  PHILOSOPHY  OF  REID.  243 

any  of  them  draws  his  attention,  it  draws  his  eyes  at  the 
same  time  ;  and,  as  soon  as  the  eyes  are  turned  towards 
it,  it  appears  single.  But,  in  order  to  see  things  double 
— at  least,  in  order  to  have  any  reflection  or  remembrance 
that  he  did  so — it  is  necessary  that  he  should  look  at  one 
object,  and  at  the  same  time  attend  to  the  faint  appear- 
ance of  other  objects  which  are  within  the  field  of  vision. 
This  is  a  practice  which  perhaps  he  never  used,  nor  at- 
tempted ;  and  therefore  he  does  not  recollect  that  ever 
he  saw  an  object  double.  But  when  he  is  put  upon  giv- 
ing this  attention,  he  immediately  sees  objects  double, 
in  the  same  manner,  and  with  the  very  same  circum- 
stances, as  they  who  have  been  accustomed,  for  the 
greatest  part  of  their  lives,  to  give  this  attention. 

There  are  many  phenomena  of  a  similar  nature,  which 
shew  that  the  mind  may  not  attend  to,  and  thereby,  in 
some  sort,  not  perceive  objects  that  strike  the  senses.  I 
had  occasion  to  mention  several  instances  of  this  in  the 
second  chapter;  and  I  have  been  assured,  by  persons  of 
the  best  skill  in  music,  that,  in  hearing  a  tune  upon  the 
harpsichord,  when  they  give  attention  to  the  treble,  they 
do  not  hear  the  bass;  and  when  they  attend  to  the  bass, 
they  do  not  perceive  the  air  of  the  treble.  Some  persons 
are  so  near-sighted,  that,  in  reading,  they  hold  the  book 
to  one  eye,  while  the  other  is  directed  to  other  objects. 
Such  persons  acquire  the  habit  of  attending,  in  this  case, 
to  the  objects  of  one  eye,  while  they  give  no  attention  to 
those  of  the  other. 

6.  It  is  observable,  that,  in  all  cases,  wherein  we  see 
an  object  double,  the  two  appearances  have  a  certain 
position  with  regard  to  one  another,  and  a  certain  ap- 
parent or  angular  distance.  This  apparent  distance  is 
greater  or  less  in  different  circumstances  ;  but,  in  the  same 
circumstances,  it  is  always  the  same,  not  only  to  the 
same,  but  to  different  persons. 

Thus,  in  the  experiment  above  mentioned,  if  twenty 
different  persons,  who  see  perfectly  with  both  eyes,  shall 


244  THE  PHILOSOPHY   OF   REID.  [Cn.  VI. 

place  their  finger  and  the  candle  at  the  distances  above 
expressed,  and  hold  their  heads  upright,  looking  at  the 
finger,  they  will  see  two  candles,  one  on  the  right,  another 
on  the  left.  That  which  is  seen  on  the  right,  is  seen  by 
the  right  eye,  and  that  which  is  seen  on  the  left,  by  the 
left  eye;  and  they  will  see  them  at  the  same  apparent  dis- 
tance from  each  other.  If,  again,  they  look  at  the  candle, 
they  will  see  two  fingers,  one  on  the  right,  and  the  other 
on  the  left ;  and  all  will  see  them  at  the  same  apparent 
distance ;  the  finger  towards  the  left  being  seen  by  the 
right  eye,  and  the  other  by  the  left.  If  the  head  is  laid 
horizontally  to  one  side,  other  circumstances  remaining 
the  same,  one  appearance  of  the  object  seen  double,  will 
be  directly  above  the  other.  In  a  word,  vary  the  cir- 
cumstances as  you  please,  and  the  appearances  are  varied 
to  all  the  spectators  in  one  and  the  same  manner. 

7.  Having   made   many  experiments  in  order  to  as- 
certain the  apparent  distance  of  the  two  appearances  of  an 
object  seen  double,  I  have  found  that  in  all  cases  this 
apparent  distance  is  proportioned  to  the  distance  between 
the  point  of  the  retina,  where  the  picture  is  made  in  one 
eye,  and  the  point  which  is  situated  similarly  to  that  on 
which  the  picture  is  made  on  the  other  eye ;  so  that,  as 
the  apparent  distance  of  two  objects  seen  with  one  eye, 
is  proportioned  to  the  arch  of  the  retina,  which  lies  be- 
tween their  pictures,  in  like  manner,  when  an  object  is 
seen  double  with  the  two  eyes,  the  apparent  distance  of 
the  two  appearances  is  proportioned  to  the  arch  of  either 
retina,  which  lies  between  the  picture  in  that  retina,  and 
the   point  corresponding  to   that  of  the  picture  in  the 
other  retina. 

8.  As,  in  certain  circumstances,  we  invariably  see  one 
obect  appear  double,  so,  in  others,  we  as  invariably  see 
two  objects  unite  into  one,  and,  in  appearance,  lose  their 
duplicity.     This   is   evident   in  the  appearance   of  the 
binocular  telescope.     And  the  same  thing  happens  when 
any  two  similar  tubes  are  applied  to  the  two  eyes  in  a 


SEC.  XIII.]  THE  PHILOSOPHY  OF  REID.  245 

parallel  direction;  for,  in  this  case,  we  see  only  one  tube. 
And  if  two  shillings  are  placed  at  the  extremities  of  the 
two  tubes,  one  exactly  in  the  axis  of  one  eye,  and  the 
other  in  the  axis  of  the  other  eye,  we  shall  see  but  one 
shilling.  If  two  pieces  of  coin,  or  other  bodies,  of  dif- 
ferent colour,  and  of  different  figure  be  properly  placed 
in  the  two  axes  of  the  eyes,  and  at  the  extremities  of  the 
tubes,  we  shall  see  both  the  bodies  in  one  and  the  same 
place,  each  as  it  were  spread  over  the  other,  without  hid- 
ing it ;  and  the  colour  will  be  that  which  is  compounded 
of  the  two  colours. 

9.  From  these  phenomena,  and  from  all  the  trials  I 
have  been  able  to  make,  it  appears  evidently,  that,  in 
perfect  human  eyes,  the  centres  of  the  two  retina  cor- 
respond and  harmonize  with  one  another,  and  that  every 
other  point  in  one  retina  doth  correspond  and  harmonize 
with  the  point  which  is  similarly  situate  in  the  other- 
in  such  manner,  that  pictures  falling  on  the  corresponding 
points  of  the  t  wo  retina,  shew  only  one  object,  even  when 
there  are  really  two;  and  pictures  falling  upon  points  of 
the  retina  which  do  not  correspond,  shew  us  two  visible 
appearances,  although  there  be  but  one  object:  so  that 
pictures,  upon  corresponding  points  of  the  two  retina, 
present  the  same  appearance  to  the  mind  as  if  they  had 
both  fallen  upon  the  same  point  of  one  retina;  and 
pictures  upon  points  of  the  two  retina,  which  do  not 
correspond,  present  to  the  mind  the  same  apparent  dis- 
tance and  position  of  two  objects,  as  if  one  of  those 
pictures  was  carried  to  the  point  corresponding  to  it  in 
the  other  retina.  This  relation  and  sympathy  between 
corresponding  points  of  the  two  retina,  I  do  not  advance 
as  an  hypothesis,  but  as  a  general  fact  or  phenomenon 
of  vision.  All  the  phaenomena  before  mentioned,  of 
single  or  double  vision,  lead  to  it,  and  are  necessary 
consequences  of  it.  It  holds  true  invariably  in  all  per- 
fect human  eyes,  as  far  as  I  am  able  to  collect  from  in- 
numerable trials  of  various  kinds  made  upon  my  own 


246  THE  PHILOSOPHY   OF   REID.  [CH.  VI. 

eyes,  and  many  made  by  others  at  my  desire.  Most  of 
the  hypotheses  that  have  been  contrived  to  resolve  the 
phenomena  of  single  and  double  vision,  suppose  this 
general  fact,  while  their  authors  were  not  aware  of  it. 
Sir  Isaac  Newton,  who  was  too  judicious  a  philosopher, 
and  too  accurate  an  observer,  to  have  offered  even  a 
conjecture  which  did  not  tally  with  the  facts  that  had 
fallen  under  his  observation,  proposes  a  query  with  re- 
spect to  the  cause  of  it — ' '  Optics, "  Query,  1 5.  The  judi- 
cious Dr.  Smith,  in  his  "Optics,"  Book  I,  §  137,  hath 
confirmed  the  truth  of  this  general  phenomenon  from 
his  own  experience,  not  only  as  to  the  apparent  unity  of 
objects  whose  pictures  fall  upon  the  corresponding  points 
of  the  retince,  but  also  as  to  the  apparent  distance  of  the 
two  appearances  of  the  same  object  when  seen  double. 

This  general  phaenomenon  appears,  therefore,  to  be 
founded  upon  a  very  full  induction,  which  is  all  the  evi- 
dence we  can  have  for  a  fact  of  this  nature.  Before  we 
make  an  end  of  this  subject,  it  will  be  proper  to  inquire, 
First,  Whether  those  animals  whose  eyes  have  an  adverse 
position  in  their  heads,  and  look  contrary  ways,  have 
such  corresponding  points  in  their  retina?  Secondly, 
What  is  the  position  of  the  corresponding  points  in  im- 
perfect human  eyes — I  mean  in  those  that  squint  ?  And, 
in  the  last  place,  Whether  this  harmony  of  the  corre- 
sponding points  in  the  retince,  be  natural  and  original,  or 
the  effect  of  custom  ?  And,  if  it  is  original,  Whether  it 
can  be  accounted  for  by  any  of  the  laws  of  nature  al- 
ready discovered  ?  or  whether  it  is  itself  to  be  looked 
upon  as  a  law  of  nature,  and  a  part  of  the  human  con- 
stitution ? 

Section   XIV. 

OF   THE    LAWS    OF   VISION    IN    BRUTE    ANIMALS. 

It  is  the  intention  of  nature,  in  giving  eyes  to  animals, 
that  they  may  perceive  the  situation  of  visible  objects, 
or  the  direction  in  which  they  are  placed — it  is  probable, 


SEC.  XIV.]  THE  PHILOSOPHY   OF  REID.  247 

therefore,  that,  in  ordinary  cases,  every  animal,  whether 
it  has  many  eyes  or  few,  whether  of  one  structure  or  of 
another,  sees  objects  single,  and  in  their  true  and  pro- 
per direction.  And,  since  there  is  a  prodigious  variety 
in  the  structure,  the  motions,  and  the  number  of  eyes  in 
different  animals  and  insects,  it  is  probable  that  the  laws 
by  which  vision  is  regulated,  are  not  the  same  in  all,  but 
various,  'adapted  to  the  eyes  which  nature  hath  given 
them. 

Mankind  naturally  turn  their  eyes  always  the  same 
way,  so  that  the  axes  of  the  two  eyes  meet  in  one  point. 
They  naturally  attend  to,  or  look  at  that  object  only 
which  is  placed  in  the  point  where  the  axes  meet.  And 
whether  the  object  be  more  or  less  distant,  the  configu- 
ration of  the  eye  is  adapted  to  the  distance  of  the  object, 
so  as  to  form  a  distinct  picture  of  it. 

When  we  use  our  eyes  in  this  natural  way,  the  two 
pictures  of  the  object  we  look  at  are  formed  upon  the 
centres  of  the  two  retince;  and  the  two  pictures  of  any 
contiguous  object  are  formed  upon  the  points  of  the 
retince  which  are  similarly  situate  with  regard  to  the 
centres.  Therefore,  in  order  to  our  seeing  objects  single, 
and  in  their  proper  direction,  with  two  eyes,  it  is  suffi- 
cient that  we  be  so  constituted,  that  objects  whose  pictures 
are  formed  upon  the  centres  of  the  two  retince,  or  upon 
points  similarly  situate  with  regard  to  these  centres,  shall 
be  seen  in  the  same  visible  place.  And  this  is  the  con- 
stitution which  nature  hath  actually  given  to  human 
eyes. 

When  we  distort  our  eyes  from  their  parallel  direction, 
which  is  an  unnatural  motion,  but  may  be  learned  by 
practice;  or  when  we  direct  the  axes  of  the  two  eyes  to 
one  point,  and  at  the  same  time  direct  our  attention  to 
some  visible  object  much  nearer  or  much  more  distant 
than  that  point,  which  is  also  unnatural,  yet  may  be 
learned :  in  these  cases,  and  in  these  only,  we  see  one  ob- 
ject double,  or  two  objects  confounded  in  one.  In  these 


248  THE  PHILOSOPHY  OF  REID.  [CH.  VI. 

cases,  the  two  pictures  of  the  same  object  are  formed 
upon  points  of  the  retina  which  are  not  similarly  sit- 
uate, and  so  the  object  is  seen  double;  or  the  two  pic- 
tures of  different  objects  are  formed  upon  points  of  the 
refines  which  are  similarly  situate,  and  so  the  two  ob- 
jects are  seen  confounded  in  one  place. 

Thus  it  appears,  that  the  laws  of  vision  in  the  human 
constitution  are  wisely  adapted  to  the  natural  use  of 
human  eyes,  but  not  to  that  use  of  them  which  is  un- 
natural. We  see  objects  truly  when  we  use  our  eyes  in 
the  natural  way;  but  have  false  appearances  presented  to 
us  when  we  use  them  in  a  way  that  is  unnatural.  We 
may  reasonably  think  that  the  case  is  the  same  with 
other  animals.  But  is  it  not  unreasonable  to  think,  that 
those  animals  which  naturally  turn  one  eye  towards  one 
object,  and  another  eye  towards  another  object,  must 
thereby  have  such  false  appearances  presented  to  them, 
as  we  have  when  we  do  so  against  nature  ? 

Many  animals  have  their  eyes  by  nature  placed  ad- 
verse and  immovable,  the  axes  of  the  two  eyes  being 
always  directed  to  opposite  points.  Do  objects  painted 
on  the  centres  of  the  two  retina  appear  to  such  animals 
as  they  do  to  human  eyes,  in  one  and  the  same  visible 
place  ?  I  think  it  is  highly  probable  that  they  do  not ; 
and  that  they  appear,  as  they  really  are,  in  opposite  places. 

If  we  judge  from  analogy  in  this  case,  it  will  lead  us 
to  think  that  there  is  a  certain  correspondence  between 
points  of  the  two  retinas  in  such  animals,  but  of  a  differ- 
ent kind  from  that  which  we  have  found  in  human  eyes. 
The  centre  of  one  retina  will  correspond  with  the  centre 
of  the  other,  in  such  manner  that  the  objects  whose  pic- 
tures are  formed  upon  the  secorresponding  points,  shall 
appear  not  to  be  in  the  same  place,  as  in  human  eyes, 
but  in  opposite  places.  And  in  the  same  manner  will 
the  superior  part  of  one  retina  correspond  with  the  in- 
ferior part  of  the  other,  and  the  anterior  part  of  one  with 
the  posterior  part  of  the  other. 


SEC.  XV.]  THE  PHILOSOPHY  OF  REID.  249 

Some  animals,  by  nature,  turn  their  eyes  with  equal 
facility,  either  the  same  way  or  different  ways,  as  we  turn 
our  hands  and  arms.  Have  such  animals  corresponding 
points  in  their  retince,  and  points  which  do  not  corre- 
spond, as  the  human  kind  has  ?  I  think  it  is  probable 
that  they  have  not;  because  such  a  constitution  in  them 
could  serve  no  other  purpose  but  to  exhibit  false  appear- 
ances. 

If  we  judge  from  analogy,  it  will  lead  us  to  think, 
that,  as  such  animals  move  their  eyes  in  a  manner  sim- 
ilar to  that  in  which  we  move  our  arms,  they  have  an 
immediate  and  natural  perception  of  the  direction  they 
give  to  their  eyes,  as  we  have  of  the  directions  we  give  to 
our  arms;  and  perceive  the  situation  of  visible  objects 
by  their  eyes,  in  a  manner  similar  to  that  in  which  we 
perceive  the  situation  of  tangible  objects  with  our  hands. 

We  cannot  teach  brute  animals  to  use  their  eyes  in 
any  other  way  than  in  that  which  nature  hath  taught 
them;  nor  can  we  teach  them  to  communicate  to  us  the 
appearances  which  visible  objects  make  to  them,  either 
in  ordinary  or  in  extraordinary  cases.  We  have  not, 
therefore,  the  same  means  of  discovering  the  laws  of 
vision  in  them,  as  in  our  own  kind,  but  must  satisfy 
ourselves  with  probable  conjectures;  and  what  we  have 
said  upon  this  subject,  is  chiefly  intended  to  shew,  that 
animals  to  which  nature  hath  given  eyes  differing  in 
their  number,  in  their  position,  and  in  their  natural 
motions,  may  very  probably  be  subjected  to  different 
laws  of  vision,  adapted  to  the  peculiarities  of  their  organs 
of  vision. 

Section   XV. 

SQUINTING     CONSIDERED    HYPOTHETICALLY. 

Whether  there  be  corresponding  points  in  the  retina, 
of  those  who  have  an  involuntary  squint  ?  and  if  there 
are,  whether  they  be  situate  in  the  same  manner  as  in 


250  THE  PHILOSOPHY  OF  REID.  [CH.Vi. 

those  who  have  no  squint  ?  are  not  questions  of  mere 
curiosity.  They  are  of  real  importance  to  the  physician 
who  attempts  the  cure  of  a  squint,  and  to  the  patient  who 
submits  to  the  cure.  After  so  much  has  been  said  of  the 
strabismus,  or  squint,  both  by  medical  and  by  optical 
writers,  one  might  expect  to  find  abundance  of  facts  for 
determining  these  questions.  Yet,  I  confess,  I  have 
been  disappointed  in  this  expectation,  after  taking  some 
pains  both  to  make  observations,  and  to  collect  those 
which  have  been  made  by  others. 

Nor  will  this  appear  very  strange,  if  we  consider,  that 
to  make  the  observations  which  are  necessary  for  deter- 
mining these  questions,  knowledge  of  the  principles  of 
optics,  and  of  the  laws  of  vision,  must  concur  with 
opportunities  rarely  to  be  met  with. 

Of  those  who  squint,  the  far  greater  part  have  no  dis- 
tinct vision  with  one  eye.  When  this  is  the  case,  it  is 
impossible,  and  indeed  of  no  importance,  to  determine 
the  situation  of  the  corresponding  points.  When  both 
eyes  are  good,  they  commonly  differ  so  much  in  their 
direction,  that  the  same  object  cannot  be  seen  by  both 
at  the  same  time;  and,  in  this  case,  it  will  be  very  diffi- 
cult to  determine  the  situation  of  the  corresponding 
points;  for  such  persons  will  probably  attend  only  to  the 
objects  of  one  eye,  and  the  objects  of  the  other  will  be 
as  little  regarded  as  if  they  were  not  seen. 

We  have  before  observed,  that,  when  we  look  at  a 
near  object,  and  attend  to  it,  we  do  not  perceive  the 
double  appearances  of  more  distant  objects,  even  when 
they  are  in  the  same  direction,  and  are  presented  to  the 
eye  at  the  same  time.  It  is  probable  that  a  squinting 
person,  when  he  attends  to  the  objects  of  one  eye,  will, 
in  like  manner,  have  his  attention  totally  diverted  from 
the  objects  of  the  other;  and  that  he  will  perceive  them 
as  little  as  we  perceive  the  double  appearances  of  objects 
when  we  use  our  eyes  in  the  natural  way.  Such  a  per- 
son, therefore,  unless  he  is  so  much  a  philosopher  as  to 


SEC.  XV.]  THE  PHILOSOPHY  OF  REID.  2$! 

have  acquired  the  habit  of  attending  very  accurately  to 
the  visible  appearances  of  objects,  and  even  of  objects 
which  he  does  not  look  at,  will  not  be  able  to  give  any 
light  to  the  questions  now  under  consideration. 

It  is  very  probable  that  hares,  rabbits,  birds,  and  fishes, 
whose  eyes  are  fixed  in  an  adverse  position,  have  the 
natural  faculty  of  attending  at  the  same  time  to  visible 
objects  placed  in  different,  and  even  in  contrary  direc- 
tions; because,  without  this  faculty,  they  could  not  have 
those  advantages  from  the  contrary  direction  of  their 
eyes,  which  nature  seems  to  have  intended.  But  it  is 
not  probable  that  those  who  squint  have  any  such  natural 
faculty;  because  we  find  no  such  faculty  in  the  rest 
of  the  species.  We  naturally  attend  to  objects  placed  in 
the  point  where  the  axes  of  the  two  eyes  meet,  and  to 
them  only.  To  give  attention  to  an  object  in  a  different 
direction  is  unnatural  and  not  to  be  learned  without 
pains  and  practice. 

A  very  convincing  proof  of  this  may  be  drawn  from  a 
fact  now  well  known  to  philosophers  :  when  one  eye  is 
shut,  there  is  a  certain  space  within  the  field  of  vision, 
where  we  can  see  nothing  at  all — the  space  which  is  di- 
rectly opposed  to  that  part  of  the  bottom  of  the  eye 
where  the  optic  nerve  enters.  This  defect  of  sight,  in 
one  part  of  the  eye,  is  common  to  all  human  eyes,  and 
hath  been  so  from  the  beginning  of  the  world;  yet  it 
was  never  known,  until  the  sagacity  of  the  Abb6  Mari- 
otte  discovered  it  in  the  last  century.  And  now  when 
it  is  known,  it  cannot  be  perceived,  but  by  means  of 
some  particular  experiments,  which  require  care  and  at- 
tention to  make  them  succeed. 

What  is  the  reason  that  so  remarkable  a  defect  of 
sight,  common  to  all  mankind,  was  so  long  unknown, 
and  is  now  perceived  with  so  much  difficulty  ?  It  is 
surely  this — That  the  defect  is  at  some  distance  from  the 
axis  of  the  eye,  and  consequently  in  a  part  of  the  field 
of  vision  to  which  we  never  attend  naturally,  and  to 


2$2  THE  PHILOSOPHY  OF  REID.  [CH.  VI. 

which  we  cannot  attend  at  all,  without  the  aid  of  some 
particular  circumstances. 

From  what  we  have  said,  it  appears,  that,  to  deter- 
mine the  situation  of  the  corresponding  points  in  the 
eyes  of  those  who  squint,  is  impossible,  if  they  do  not 
see  distinctly  with  both  eyes;  and  that  it  will  be  very 
difficult,  unless  the  two  eyes  differ  so  little  in  their  di- 
rection, that  the  same  object  may  be  seen  with  both  at 
the  same  time.  Such  patients  I  apprehend  are  rare;  at 
least  there  are  very  few  of  them  with  whom  I  have  had 
the  fortune  to  meet:  and  therefore,  for  the  assistance  of 
those  who  may  have  happier  opportunities,  and  inclina- 
tion to  make  the  proper  use  of  them,  we  shall  consider 
the  case  of  squinting,  hypothetically,  pointing  out  the 
proper  articles  of  inquiry,  the  observations  that  are 
wanted,  and  the  conclusions  that  may  be  drawn  from  them. 

1.  It  ought  to  be  inquired,  Whether  the  squinting 
person  sees  equally  well  with  both  eyes  ?  and,  if  there 
be  a  defect  in  one,  the  nature  and  degree  of  that  defect 
ought  to  be  remarked.     The  experiments  by  which  this 
may  be  done,  are  so  obvious,  that  I  need  not  mention 
them.     But  I  would  advise  the  observer  to  make  the 
proper  experiments,  and  not  to  rely  upon  the  testimony 
of  the  patient;  because  I  have  found  many  instances, 
both  of  persons  that   squinted,   and  others   who  were 
found,  upon  trial,  to  have  a  great  defect  in  the  sight  of 
one  eye,  although  they  were  never  aware  of  it  before. 
In  all  the  following  articles,  it  is  supposed  that  the  patient 
sees  with  both  eyes  so  well  as  to  be  able  to  read  with 
either,  when  the  other  is  covered. 

2.  It  ought  to  be  inquired,  Whether,  when  one  eye 
is  covered,  the  other  is  turned  directly  to  the  object  ? 
This  ought  to  be  tried  in  both  eyes  successively.     By 
this  observation,  as  a  touchstone,  we  may  try  the  hy- 
pothesis concerning   squinting,  invented  by  M.    de  la 
Hire,  and  adopted  by  Boerhaave,  and  many  others  of 
the  medical  faculty. 


SEC.  XV.]  THE  PHILOSOPHY  OF  REID.  2$3 

The  hypothesis  is,  That,  in  one  eye  of  a  squinting 
person,  the  greatest  sensibility  and  the  most  distinct 
vision  is  not,  as  in  other  men,  in  the  centre  of  the  retina, 
but  upon  one  side  of  the  centre  ;  and  that  he  turns  the 
axis  of  this  eye  aside  from  the  object,  in  order  that  the 
picture  of  the  object  may  fall  upon  the  most  sensible  part 
of  the  retina,  and  thereby  give  the  most  distinct  vision. 
If  this  is  the  cause  of  squinting,  the  squinting  eye  will  be 
turned  aside  from  the  object,  when  the  other  eye  is  covered, 
as  well  as  when  it  is  not. 

A  trial  so  easy  to  be  made,  never  was  made  for  more 
than  forty  years ;  but  the  hypothesis  was  very  generally 
received — so  prone  are  men  to  invent  hypotheses,  and  so 
backward  to  examine  them  by  facts.  At  last,  Dr.  Jurin 
having  made  the  trial,  found  that  persons  who  squint  turn 
the  axis  of  the  squinting  eye  directly  to  the  object,  when 
the  other  eye  is  covered.  This  fact  is  confirmed  by  Dr. 
Porterfield ;  and  I  have  found  it  verified  in  all  the  in- 
stances that  have  fallen  under  my  observation. 

3.  It  ought  to  be  inquired,  Whether  the  axes  of  the 
two   eyes  follow  one  another,  so  as  to  have  always  the 
same  inclination,  or  make  the  same  angle,   when  the 
person  looks  to  the  right  or  to  the  left,  upward  or  down- 
ward, or  straight  forward.     By  this  observation  we  may 
judge  whether  a  squint  is  owing  to  any  defect  in  the 
muscles  which  move  the  eye,  as  some  have  supposed.     In 
the  following   articles,  we  suppose  that  the  inclination 
of  the   axes  of   the   eyes  is   found  to   be   always   the 
same. 

4.  It  ought  to  be  inquired,  Whether  the  person  that 
squints  sees  an  object  single  or  double  I 

If  he  sees  the  object  double,  and  if  the  two  appear- 
ances have  an  angular  distance,  equal  to  the  angle  which 
the  axes  of  his  eyes  make  with  each  other,  it  may  be  con- 
cluded that  he  hath  corresponding  points  in  the  retince  of 
his  eyes,  and  that  they  have  the  same  situation  as  in  those 
who  have  no  squint  If  the  two  appearances  should 


254  THE  PHILOSOPHY  OF  REID.  |Cn.  VI. 

have  an  angular  distance  which  is  always  the  same,  but 
manifestly  greater  or  less  than  the  angle  contained  under 
the  optic  axes,  this  would  indicate  corresponding  points 
in  the  retina,  whose  situation  is  not  the  same  as  in  those 
who  have  no  squint ;  but  it  is  difficult  to  judge  accurately 
of  the  angle  which  the  optic  axes  make. 

A  squint  too  small  to  be  perceived,  may  occasion 
double  vision  of  objects :  for,  if  we  speak  strictly,  every 
person  squints  more  or  less,  whose  optic  axes  do  not 
meet  exactly  in  the  object  which  he  looks  at.  Thus,  if 
a  man  can  only  bring  the  axes  of  his  eyes  to  be  parallel, 
but  cannot  make  them  converge  in  the  least,  he  must 
have  a  small  squint  in  looking  at  near  objects,  and  will 
see  them  double,  while  he  sees  very  distant  objects  single. 
Again,  if  the  optic  axes  always  converge,  so  as  to  meet 
eight  or  ten  feet  before  the  face  at  farthest,  such  a  person 
will  see  near  objects  single  ;  but  when  he  looks  at  very 
distant  objects,  he  will  squint  a  little,  and  see  them 
double. 

An  instance  of  this  kind  is  related  by  Aguilonius  in 
his  "Optics,"  who  says,  that  he  had  seen  a  young  man  to 
whom  near  objects  appeared  single,  but  distant  objects 
appeared  double. 

Dr.  Briggs,  in  his  "  Nova  Visionis  Theoria,"  having  col- 
lected from  authors  several  instances  of  double  vision, 
quotes  this  from  Aguilonius,  as  the  most  wonderful  and 
unaccountable  of  all,  insomuch  that  he  suspects  some  im- 
position on  the  part  of  the  young  man:  but  to  those  who 
understand  the  laws  by  which  single  and  double  vision  are 
regulated,  it  appears  to  be  the  natural  effect  of  a  very 
small  squint. 

Double  vision  may  always  be  owing  to  a  small  squint, 
when  the  two  appearances  are  seen  at  a  small  angular 
distance,  although  no  squint  was  observed  :  and  I  do 
not  remember  any  instances  of  double  vision  recorded  by 
authors,  wherein  any  account  is  given  of  the  angular  dis- 
tance of  the  appearances. 


SEC.  XV.]  THE  PHILOSOPHY  OF  REID.  2$$ 

In  almost  all  the  instances  of  double  vision,  there  is 
reason  to  suspect  a  squint  or  distortion  of  the  eyes,  from 
the  concomitant  circumstances,  which  we  find  to  be  one 
or  other  of  the  following — the  approach  of  death  or  of  a 
deliquium,  excessive  drinking  or  other  intemperance,  vio- 
lent headache,  blistering  the  head,  smoking  tobacco, 
blows  or  wounds  in  the  head.  In  all  these  cases,  it  is 
reasonable  to  suspect  a  distortion  of  the  eyes,  either  from 
spasm,  or  paralysis  in  the  muscles  that  move  them.  But, 
although  it  be  probable  that  there  is  always  a  squint 
greater  or  less  where  there  is  double  vision,  yet  it  is 
certain  that  there  is  not  double  vision  always  where 
there  is  a  squint.  I  know  no  instance  of  double  vision 
that  continued  for  life,  or  even  for  a  great  number  of 
years. .  We  shall  therefore  suppose,  in  the  following  arti- 
cles, that  the  squinting  person  sees  objects  single. 

5.  The  next  inquiry,  then,  ought  to  be,  Whether  the 
object  is  seen  with  both  eyes  at  the  same  time,  or  only 
with  the  eye  whose  axes  is  directed  to  it  ?  It  hath  been 
taken  for  granted,  by  the  writers  upon  the  strabismus,  be- 
fore Dr.  Jurin,  that  those  who  squint  commonly  see  ob- 
jects single  with  both  eyes  at  the  same  time  ;  but  I  know 
not  one  fact  advanced  by  any  writer  which  proves  it.  Dr. 
Jurin  is  of  a  contrary  opinion ;  and,  as  it  is  of  conse- 
quence, so  it  is  very  easy,  to  determine  this  point,  in 
particular  instances,  by  this  obvious  experiment.  While 
the  person  that  squints  looks  steadily  at  an  object,  let  the 
observer  carefully  remark  the  direction  of  both  his  eyes, 
and  observe  their  motions  ;  and  let  an  opaque  body  be 
interposed  between  the  object  and  the  two  eyes  succes- 
sively. If  the  patient,  notwithstanding  this  interposition, 
and  without  changing  the  direction  of  his  eyes,  continues 
to  see  the  object  all  the  time,  it  may  be  concluded  that 
he  saw  it  with  both  eyes  at  once.  But,  if  the  interposi- 
tion of  the  body  between  one  eye  and  the  object  makes  it 
disappear,  then  we  may  be  certain  that  it  was  seen  by 
that  eye  only.  In  the  two  following  articles,  we  shall 


256  THE  PHILOSOPHY  OF  REID.  |CH.  VI. 

suppose  the  first  to  happen,  according  to  the  common 
hypothesis. 

6.  Upon  this  supposition,  it  ought  to  be  inquired, 
Whether  the  patient  sees  an  object  double  in  those  cir- 
cumstances wherein  it  appears  double  to  them  who  have 
no  squint?     Let  him,  for  instance,  place  a  candle  at  the 
distance  of  ten  feet ;  and   holding  his  finger  at  arm's- 
length  between  him  and  the  candle,  let  him  observe, 
when  he  looks  at  the  candle,  whether  he  sees  his  finger 
with  both  eyes,  and  whether  he  sees  it  single  or  double; 
and  when  he  looks  at  his  finger,  let  him  observe  whether 
he  sees  the  candle  with  both  eyes  and  whether  single  or 
double. 

By  this  observation,  it  may  be  determined,  whether  to 
this  patient,  the  phenomena  of  double  as  well  as  of  sin- 
gle vision  are  the  same  as  to  them  who  have  no  squint. 
If  they  are  not  the  same — if  he  sees  objects  single  with 
two  eyes,  not  only  in  the  cases  wherein  they  appear  sin- 
gle, but  in  those  also  wherein  they  appear  double  to  other 
men — the  conclusion  to  be  drawn  from  this  supposition 
is,  that  his  single  vision  does  not  arise  from  corresponding 
points  in  the  retina  of  his  eyes  :  and  that  the  laws  of  vis- 
ion are  not  the  same  in  him  as  in  the  rest  of  mankind. 

7.  If,  on  the  other  hand,  he  sees  objects  double  in 
those  cases  wherein  they  appear  double  to  others,  the 
conclusion  must  be,  that  he  hath  corresponding  points 
in  the  retina  of  his  eyes,  but  unnaturally  situate.     And 
their  situation  may  be  thus  determined. 

When  he  looks  at  an  object,  having  the  axis  of  one  eye 
directed  to  it,  and  the  axis  of  the  other  turned  aside  from  it, 
let  us  suppose  a  right  line  to  pass  from  the  object  through 
the  centre  of  the  diverging  eye.  We  shall,  for  the  sake 
of  perspicuity,  call  this  right  line,  the  natural  axis  of  the 
eye ;  and  it  will  make  an  angle  with  the  real  axis,  greater 
or  less,  according  as  his  squint  is  greater  or  less.  We 
shall  also  call  that  point  of  the  retina  in  which  the  natural 
axis  cuts  it,  the  natural  centre  of  the  retina ;  which  will 


SEC.  XV.]  THE  PHILOSOPHY  OF  REID.  257 

be  more  or  less  distant  from  the  real  centre,  according 
as  the  squint  is  greater  or  less. 

Having  premised  these  definitions,  it  will  be  evident 
to  those  who  understand  the  principles  of  optics,  that  in 
this  person  the  natural  centre  of  one  retina  corresponds 
with  the  real  centre  of  the  other,  in  the  very  same  man- 
ner as  the  two  real  centres  correspond  in  perfect  eyes  ;  and 
that  the  points  similarly  situate  with  regard  to  the  real 
centre  in  one  retina,  and  the  natural  centre  in  the  other, 
do  likewise  correspond,  in  the  very  same  manner  as  the 
points  similarly  situate  with  regard  to  the  two  real  cen- 
tres correspond  in  perfect  eyes. 

If  it  is  true,  as  has  been  commonly  affirmed,  that  one 
who  squints  sees  an  object  with  both  eyes  at  the  same 
time,  and  yet  sees  it  single,  the  squint  will  most  probably 
be  such  as  we  have  described  in  this  article.  And  we 
may  further  conclude,  that,  if  a  person  affected  with  such 
a  squint  as  we  have  supposed,  could  be  brought  to  the 
habit  of  looking  straight,  his  sight  would  thereby  be 
greatly  hurt ;  for  he  would  then  see  everything  double 
which  he  saw  with  both  eyes  at  the  same  time  ;  and  ob- 
jects distant  from  one  another  would  appear  to  be  con- 
founded together.  His  eyes  are  made  for  squinting,  as 
much  as  those  of  other  men  are  made  for  looking  straight; 
and  his  sight  would  be  no  less  injured  by  looking  straight, 
than  that  of  another  man  by  squinting.  He  can  never 
see  perfectly  when  he  does  not  squint,  unless  the  corre- 
sponding points  of  his  eyes  should  by  custom  change 
their  place  ;  but  how  small  the  probability  of  this  is  will 
appear  in  the  i  yth  section. 

Those  of  the  medical  faculty  who  attempt  the  cure  of 
a  squint,  would  do  well  to  consider  whether  it  is  attended 
with  such  symptoms  as  are  above  described.  If  it  is, 
the  cure  would  be  worse  than  the  malady:  for,  everyone 
will  readily  acknowledge  that  it  is  better  to  put  up  with 
the  deformity  of  a  squint,  than  to  purchase  the  cure  by 
the  loss  of  perfect  and  distinct  vision. 


258  THE  PHILOSOPHY  OF  REID.  [Cn.  VI. 

8.  We  shall  now  return  to  Dr.  Jurin's  hypothesis,  and 
suppose  that  our  patient,  when  he  saw  objects  single 
notwithstanding  his  squint,  was  found,  upon  trial,  to  have 
seen  them  only  with  one  eye. 

We  would  advise  such  a  patient  to  endeavor,  by  re- 
peated efforts,  to  lessen  his  squint,  and  to  bring  the  axes 
of  his  eyes  nearer  to  a  parallel  direction.  We  have  natu- 
rally the  power  of  making  small  variations  in  the  inclina- 
tion of  the  optic  axes  ;  and  this  power  may  be  greatly  in- 
creased by  exercise. 

In  the  ordinary  and  natural  use  of  our  eyes,  we  can 
direct  their  axes  to  a  fixed  star;  in  this  case  they  must 
be  parallel:  we  can  direct  them  also  to  an  object  six 
inches  distant  from  the  eye;  and  in  this  case  the  axes 
must  make  an  angle  of  fifteen  or  twenty  degrees.  We 
see  young  people  in  their  frolics  learn  to  squint,  making 
their  eyes  either  converge  or  diverge,  when  they  will,  to 
a  very  considerable  degree.  Why  should  it  be  more 
difficult  for  a  squinting  person  to  learn  to  look  straight 
when  he  pleases?  If  once,  by  an  eifort  of  his  will,  he 
can  but  lessen  his  squint,  frequent  practice  will  make  it 
easy  to  lessen  it,  and  will  daily  increase  his  power.  So 
that,  if  he  begins  this  practice  in  youth,  and  perseveres  in 
it,  he  may  probably,  after  some  time,  learn  to  direct  both 
his  eyes  to  one  object. 

When  he  hath  acquired  this  power,  it  will  be  no  diffi- 
cult matter  to  determine,  by  proper  observations,  whether 
the  centres  of  the  retina,  and  other  points  similarly  sit- 
uate with  regard  to  the  centres,  correspond,  as  in  other 
men. 

9.  Let  us  now  suppose  that  he  finds  this  to  be  the 
case  ;  and  that  he  sees  an  object  single  with  both  eyes, 
when  the  axes  of  both  are  directed  to  it.  It  will  then 
concern  him  to  acquire  the  habit  of  looking  straight,  as 
he  hath  got  the  power,  because  he  will  thereby  not  only 
remove  a  deformity,  but  improve  his  sight ;  and  I  con- 
ceive this  habit,  like  all  others,  may  be  got  by  frequent 


SEC.  XV.]  THE  PHILOSOPHY  OF  REID.  259 

exercise.  He  may  practise  before  a  mirror  when  alone, 
and  in  company  he  ought  to  have  those  about  him  who 
will  observe  and  admonish  him  when  he  squints. 

10.  What  is  supposed  in  the  9th  article  is  not  merely 
imaginary ;  it  is  really  the  case  of  some  squinting  per- 
sons, as  will  appear  in  the  next  section.     Therefore,  it 
ought  further  to  be  inquired,  How  it  comes  to  pass  that 
such  a  person  sees  an  object  which  he  looks  at,  only 
with  one  eye,  when  both  are  open  ?     In  order  to  answer 
this  question,  it  may  be  observed,  first,  Whether,  when 
he  looks  at  an  object,  the  diverging  eye  is  not  drawn  so 
close  to  the  nose,  that  it  can  have  no  distinct  images  ? 
Or,  secondly,  whether  the  pupil  of  the  diverging  eye  is  not 
covered  wholly,  or  in'part,  by  the  upper  eyelid  ?    Dr.  Jurin 
observed  instances  of  these  cases  in  persons  that  squinted, 
and  assigns  them  as  causes  of  their  seeing  the  object  only 
with  one  eye.     Thirdly,  it  may  be  observed,  whether  the 
diverging  eye  is  not  so  directed,  that  the  picture  of  the 
object  falls  upon  that  part  of  the  retina  where  the  optic 
nerve  enters,  and  where  there  is  no  vision  ?     This  will 
probably  happen  in  a  squint  wherein  the  axes  of  the  eyes 
converge  so  as  to  meet  about  six  inches  before  the  nose. 

11.  In  the  last  place,  it  ought  to  be  inquired,  Whether 
such  a  person  hath  any  distinct  vision  at  all  with  the  di- 
verging eye,  at  the  time  he  is  looking  at  an  object  with 
the  other  ? 

It  may  seem  very  improbable  that  he  should  be  able 
to  read  with  the  diverging  eye  when  the  other  is  covered, 
and  yet,  when  both  are  open,  have  no  distinct  vision  with 
it  at  all.  But  this,  perhaps,  will  not  appear  so  improb- 
able if  the  following  considerations  are  duly  attended  to. 

Let  us  suppose  that  one  who  saw  perfectly,  gets,  by 
a  blow  on  the  head,  or  some  other  accident,  a  perma- 
nent and  involuntary  squint.  According  to  the  laws  of 
vision,  he  will  see  objects  double,  and  will  see  objects 
distant  from  one  another  confounded  together  ;  but, 
such  vision  being  very  disagreeable,  as  well  as  incon- 


260  THE  PHILOSOPHY  OF  REID.  [Ca.  VI. 

venient,  he  will  do  everything  in  his  power  to  remedy  it. 
For  alleviating  such  distresses,  nature  often  teaches  men 
wonderful  expedients,  which  the  sagacity  of  a  philoso- 
pher would  be  unable  to  discover.  Every  accidental 
motion,  every  direction  or  conformation  of  his  eyes, 
which  lessens  the  evil,  will  be  agreeable  ;  it  will  be  re- 
peated until  it  be  learned  to  perfection,  and  become  ha- 
bitual, even  without  thought  or  design.  Now,  in  this 
case,  what  disturbs  the  sight  of  one  eye  is  the  sight  of 
the  other  ;  and  all  the  disagreeable  appearances  in  vision 
would  cease  if  the  light  of  one  eye  was  extinct.  The 
sight  of  one  eye  will  become  more  distinct  and  more 
agreeable,  in  the  same  proportion  as  that  of  the  other 
becomes  faint  and  indistinct.  It  may,  therefore,  be  ex- 
pected, that  every  habit  will,  by  degrees,  be  acquired 
which  tends  to  destroy  distinct  vision  in  one  eye  while 
it  is  preserved  in  the  other.  These  habits  will  be  greatly 
facilitated  if  one  eye  was  at  first  better  than  the  other  ; 
for,  in  that  case,  the  best  eye  will  always  be  directed  to 
the  object  which  he  intends  to  look  at,  and  every  habit 
will  be  acquired  which  tends  to  hinder  his  seeing  it  at  all, 
or  seeing  it  distinctly  by  the  other  at  the  same  time. 

I  shall  mention  one  or  two  habits  that  may  probably 
be  acquired  in  such  a  case  ;  perhaps  there  are  others 
which  we  cannot  so  easily  conjecture.  First,  By  a  small 
increase  or  diminution  of  his  squint,  he  may  bring  it  to 
correspond  with  one  or  other  of  the  cases  mentioned  in 
the  last  article.  Secondly,  The  diverging  eye  may  be 
brought  to  such  a  conformation  as  to  be  extremely 
short-sighted,  and  consequently  to  have  no  distinct  vision 
of  objects  at  a  distance.  I  knew  this  to  be  the  case  of 
one  person  that  squinted  ;  but  cannot  say  whether  the 
short-sightedness  of  the  diverging  eye  was  original,  or 
acquired  by  habit. 

We  see,  therefore,  that  one  who  squints,  and  originally 
saw  objects  double  by  reason  of  that  squint,  may  acquire 
such  habits  that,  when  he  looks  at  an  object,  he  shall  see 


SEC.  XVI.]  THE  PHILOSOPHY  OF  REID.  26l 

it  only  with  one  eye ;  nay,  he  may  acquire  such  habits 
that,  when  he  looks  at  an  object  with  his  best  eye,  he 
shall  have  no  distinct  vision  with  the  other  at  all. 
Whether  this  is  really  the  case — being  unable  to  deter- 
mine in  the  instances  that  have  fallen  under  my  observa- 
tion— I  shall  leave  to  future  inquiry. 

I  have  endeavoured,  in  the  foregoing  articles,  to  de- 
lineate such  a  process  as  is  proper  in  observing  the  phae- 
nomena  of  squinting.  I  know  well  by  experience,  that 
this  process  appears  more  easy  in  theory  than  it  will  be 
found  to  be  in  practice;  and  that,  in  order  to  carry  it  on 
with  success,  some  qualifications  of  mind  are  neces- 
sary in  the  patient,  which  are  not  always  to  be  met  with. 
But,  if  those  who  have  proper  opportunities  and  incli- 
nation to  observe  such  phenomena,  attend  duly  to  this 
process,  they  may  be  able  to  furnish  facts  less  vague  and 
uninstructive  than  those  we  meet  with,  even  in  authors 
of  reputation.  '  By  such  facts,  vain  theories  may  be  ex- 
ploded, and  our  knowledge  of  the  laws  of  nature,  which 
regard  the  noblest  of  our  senses,  enlarged. 


Section  XVI. 

FACTS  RELATING  TO  SQUINTING. 

Having  considered  the  phenomena  of  squinting, 
hypothetically,  and  their  connection  with  correspond- 
ing points  in  the  retince.  I  shall  now  mention  the  facts  I 
have  had  occasion  to  observe  myself,  or  have  met  with 
in  authors,  that  can  give  any  light  to  this  subject. 

Having  examined  above  twenty  persons  that  squinted, 
I  found  in  all  of  them  a  defect  in  the  sight  of  one  eye. 
Four  only  had  so  much  of  distinct  vision  in  the  weak  eye, 
as  to  be  able  to  read  with  it,  when  the  other  was  cov- 
ered. The  rest  saw  nothing  at  all  distinctly  with  one 
eye. 

Dr.  Porterfield  says,  that  this  is  generally  the  case  of 


262  THE  PHILOSOPHY  OF  REID.  tCH.  VI. 

people  that  squint ;  and  I  suspect  it  is  so  more  generally 
than  is  commonly  imagined.  Dr.  Jurin,  in  a  very  judi- 
cious dissertation  upon  squinting,  printed  in  Dr.  Smith's 
''Optics/'  observes,  that  those  who  squint,  and  see  with 
both  eyes,  never  see  the  same  object  with  both  at  the 
same  time  ;  that,  when  one  eye  is  directed  straight  for- 
ward to  an  object,  the  other  is  drawn  so  close  to  the  nose 
that  the  object  cannot  at  all  be  seen  by  it,  the  images 
being  too  oblique  and  too  indistinct  to  affect  the  eye. 
In  some  squinting  persons,  he  observed  the  diverging 
eye  drawn  under  the  upper  eyelid,  while  the  other  was 
directed  to  the  object.  From  these  observations,  he 
concludes  that  "  the  eye  is  thus  distorted,  not  for  the 
sake  of  seeing  better  with  it,  but  rather  to  avoid  seeing 
at  all  with  it  as  much  as  possible."  From  all  the  ob- 
servations he  had  made,  he  was  satisfied  that  there  is 
nothing  peculiar  in  the  structure  of  a  squinting  eye; 
that  the  fault  is  only  in  its  wrong  direction  ;  and  that 
this  wrong  direction  is  got  by  habit.  Therefore,  he 
proposes  that  method  of  cure  which  we  have  described 
in  the  eighth  and  ninth  articles  of  the  last  section.  He 
tells  us,  that  he  had  attempted  a  cure,  after  this  method, 
upon  a  young  gentleman,  with  promising  hopes  of  suc- 
cess ;  but  was  interrupted  by  his  falling  ill  of  the  small- 
pox, of  which  he  died. 

It  were  to  be  wished  that  Dr.  Jurin  had  acquainted  us 
whether  he  ever  brought  the  young  man  to  direct  the  axes 
of  both  eyes  to  the  same  object,  and  whether,  in  that  case, 
he  saw  the  object  single,  and  saw  it  with  both  eyes  ;  and 
that  he  had  likewise  acquainted  us,  whether  he  saw  ob- 
jects double  when  his  squint  was  diminished.  But  as  to 
these  facts  he  is  silent. 

I  wished  long  for  an  opportunity  of  trying  Dr.  Jurin's 
method  of  curing  a  squint,  without  finding  one  ;  having 
always,  upon  examination,  discovered  so  great  a  defect 
in  the  sight  of  one  eye  of  the  patient  as  discouraged  the 
attempt. 


SEC.  XVI.]  THE  PHILOSOPHY   OF  REID.  263 

But  I  have  lately  found  three  young  gentlemen,  with 
whom  I  am  hopeful  this  method  may  have  success,  if 
they  have  patience  and  perseverance  in  using  it.  Two 
of  them  are  brothers,  and,  before  I  had  access  to  ex- 
amine them,  had  been  practising  this  method  by  the  di- 
rection of  their  tutor,  with  such  success,  that  the  elder 
looks  straight  when  he  is  upon  his  guard  ;  the  younger 
can  direct  both  his  eyes  to  one  object ;  but  they  soon 
return  to  their  usual  squint. 

A  third  young  gentleman,  who  had  never  heard  of  this 
method  before,  by  a  few  days'  practice,  was  able  to  di- 
rect both  his  eyes  to  one  object,  but  could  noj;  keep  them 
long  in  that  direction.  All  the  three  agree  in  this,  that, 
when  both  eyes  are  directed  to  one  object,  they  see  it 
and  the  adjacent  objects  single  ;  but,  when  they  squint, 
they  see  objects  sometimes  single  and  sometimes  double. 
I  observed  of  all  the  three,  that  when  they  squinted  most 
— that  is,  in  the  way  they  had  been  accustomed  to — the 
axes  of  their  eyes  converged  so  as  to  meet  five  or  six 
inches  before  the  nose.  It  is  probable  that,  in  this  case, 
the  picture  of  the  object  in  the  diverging  eye,  must  fall 
upon  that  part  of  the  retina  where  the  optic  nerve  enters; 
and  therefore,  the  object  could  not  be  seen  by  the  eye. 

All  the  three  have  some  defect  in  the  sight  of  one  eye, 
which  none  of  them  knew  until  I  put  them  upon  making 
trials;  and  when  they  squint,  the  best  eye  is  always 
directed  to  the  object,  and  the  weak  eye  is  that  which 
diverges  from  it.  But  when  the  best  eye  is  covered,  the 
weak  eye  is  turned  directly  to  the  object.  Whether  this 
defect  of  sight  in  one  eye,  be  the  effect  of  its  having  been 
long  disused,  as  it  must  have  been  when  they  squinted; 
or  whether  some  original  defect  in  one  eye  might  be  the 
occasion  of  their  squinting,  time  may  discover.  The 
two  brothers  have  found  the  sight  of  the  weak  eye  im- 
proved by  using  to  read  with  it  while  the  other  is  covered. 
The  elder  can  read  an  ordinary  print  with  the  weak  eye  • 
the  other,  as  well  as  the  third  gentleman,  can  only  read 


264  THE  PHILOSOPHY  OF  REID.  [Cn.  VL 

a  large  print  with  the  weak  eye.  I  have  met  with  one 
other  person  only  who  squinted,  and  yet  could  read  a  large 
print  with  the  weak  eye.  He  is  a  young  man,  whose 
eyes  are  both  tender  and  weak-sighted,  but  the  left  much 
weaker  than  the  right.  When  he  looks  at  any  object,  he  al- 
ways directs  the  right  eye  to  it,  and  then  the  left  is  turned 
towards  the  nose  so  much  that  it  is  impossible  for  him 
to  see  the  same  object  with  both  eyes  at  the  same  time. 
When  the  right  eye  is  covered,  he  turns  the  left  directly 
to  the  object;  but  he  sees  it  indistinctly,  and  as  if  it  had 
a  mist  about  it. 

I  made  several  experiments,  some  of  them  in  the  com- 
pany and  with  the  assistance  of  an  ingenious  physician, 
in  order  to  discover  whether  objects  that  were  in  the  axes 
of  the  two  eyes,  were  seen  in  one  place  confounded  to- 
gether, as  in  those  who  have  no  involuntary  squint.  The 
object  placed  in  the  axis  of  the  weak  eye  was  a  lighted 
candle,  at  the  distance  of  eight  or  ten  feet.  Before  the 
other  eye  was  placed  a  printed  book,  at  such  a  distance 
as  that  he  could  read  upon  it.  He  said,  that  while  he 
read  upon  the  book,  he  saw  the  candle  but  very  faintly. 
And  from  what  we  could  learn,  these  two  objects  did 
not  appear  in  one  place,  but  had  all  that  angular  dis- 
tance in  appearance  which  they  had  in  reality. 

If  this  was  really  the  case,  the  conclusion  to  be  drawn 
from  it  is,  that  the  corresponding  points  in  his  eyes  are 
not  situate  in  the  same  manner  as  in  other  men;  and 
that,  if  he  could  be  brought  to  direct  both  eyes  to  one 
object,  he  would  see  it  double.  But,  considering  that 
the  young  man  had  never  been  accustomed  to  observa- 
tions of  this  kind,  and  that  the  sight  of  one  eye  was  so 
imperfect,  I  do  not  pretend  to  draw  this  conclusion  with 
certainty  from  this  single  instance. 

All  that  can  be  inferred  from  these  facts  is,  that,  of 
four  persons  who  squint,  three  appear  to  have  nothing 
preternatural  in  the  structure  of  their  eyes.  The  cen- 
tres of  their  r$tin<z,  and  the  points  similarly  situate  with 


SEC.  xvii.]          THE  PHILOSOPHY  OF  REID.  265 

regard  to  the  centres,  do  certainly  correspond  in  the  same 
manner  as  in  other  men — so  that,  if  they  can  be  brought 
to  the  habit  of  directing  their  eyes  right  to  an  object, 
they  will  not  only  remove  a  deformity,  but  improve  their 
sight.  With  regard  to  the  fourth,  the  case  is  dubious, 
with  some  probability  of  a  deviation  from  the  usual 
course  of  nature  in  the  situation  of  the  corresponding 
points  of  his  eyes. 

Section  XVII. 

OF  THE  EFFECT  OF  CUSTOM  IN  SEEING  OBJECTS  SINGLE. 

It  appears  from  the  phenomena  of  single  and  double 
vision,  recited  in  §  13,  that  our  seeing  an  objec.t  single 
with  two  eyes,  depends  upon  these  two  things: — First, 
Upon  that  mutual  correspondence  of  certain  points  of 
the  retina  which  we  have  often  described;  Secondly,  Upon 
the  two  eyes  being  directed  to  the  object  so  accurately 
that  the  two  images  of  it  fall  upon  corresponding  points. 
These  two  things  must  concur  in  order  to  our  seeing  an 
object  single  with  two  eyes;  and,  as  far  as  they  depend 
upon  custom,  so  far  only  can  single  vision  depend  upon 
custom. 

With  regard  to  the  second — that  is,  the  accurate  direc- 
tion of  both  eyes  to  the  object — I  think  it  must  be  ac- 
knowledged that  this  is  only  learned  by  custom.  Na- 
ture hath  wisely  ordained  the  eyes  to  move  in  such  man- 
ner that  their  axes  shall  always  be  nearly  parallel;  but 
hath  left  it  in  our  power  to  vary  their  inclination  a  lit- 
tle, according  to  the  distance  of  the  object  we  look  at. 
Without  this  power,  objects  could  appear  single  at  one 
particular  distance  only;  and,  at  distances  much  less  or 
much  greater,  would  always  appear  double.  The  wis- 
dom of  nature  is  conspicuous  in  giving  us  this  power, 
and  no  less  conspicuous  in  making  the  extent  of  it 
exactly  adequate  to  the  end. 


266  THE  PHILOSOPHY  OF  REID.  [Cn.  VI. 

The  parallelism  of  the  eyes,  in  general,  is  therefore 
the  work  of  nature;  but  that  precise  and  accurate  direc- 
tion, which  must  be  varied  according  to  the  distance  of 
the  object,  is  the  effect  of  custom.  The  power  which 
nature  hath  left  us  of  varying  the  inclination  of  the  optic 
axes  a  little,  is  turned  into  a  habit  of  giving  them  always 
that  inclination  which  is  adapted  to  the  distance  of  the 
object. 

But  it  may  be  asked,  What  gives  rise  to  this  habit  ? 
The  only  answer  that  can  be  given  to  this  question  is, 
that  it  is  found  necessary  to  perfect  and  distinct  vision. 
A  man  who  hath  lost  the  sight  of  one  eye,  very  often 
loses  the  habit  of  directing  it  exactly  to  the  object  he  looks 
at,  because  that  habit  is  no  longer  of  use  to  him.  And 
if  he  should  recover  the  sight  of  his  eye,  he  would  re- 
cover this  habit,  by  finding  it  useful.  No  part  of  the 
human  constitution  is  more  admirable  than  that  whereby 
we  acquire  habits  which  are  found  useful,  without  any 
design  or  intention.  Children  must  see  imperfectly  at 
first;  but,  by  using  their  eyes,  they  learn  to  use  them  in 
the  best  manner,  and  acquire,  without  intending  it,  the 
habits  necessary  for  that  purpose.  Every  man  becomes 
most  expert  in  that  kind  of  vision  which  is  most  useful 
to  him  in  his  particular  profession  and  manner  of  life.  A 
miniature  painter,  or  an  engraver,  sees  very  near  objects 
better  than  a  sailor;  but  the  sailor  sees  very  distant  ob- 
jects much  better  than  they.  A  person  that  is  short- 
sighted, in  looking  at  distant  objects,  gets  the  habit  of 
contracting  the  aperture  of  his  eyes,  by  almost  closing 
his  eyelids.  Why  ?  For  no  other  reason,  but  because 
this  makes  him  see  the  object  more  distinct.  In  like 
manner,  the  reason  why  every  man  acquires  the  habit 
of  directing  both  eyes  accurately  to  the  object,  must 
be,  because  thereby  he  sees  it  more  perfectly  and  dis- 
tinctly. 

It  remains  to  be  considered,  whether  that  correspond- 
ence between  certain  points  of  the  retince,  which  is  like- 


SEC.  XVII.]  THE  PHILOSOPHY  OF  REID.  267 

wise  necessary  to  single  vision,  be  the  effect  of  custom, 
or  an  original  property  of  human  eyes. 

A  strong  argument  for  its  being  an  original  property, 
may  be  drawn  from  the  habit,  just  now  mentioned,  of 
directing  the  eyes  accurately  to  an  object.  This  habit 
is  got  by  our  finding  it  necessary  to  perfect  and  distinct 
vision.  But  why  is  it  necessary  ?  For  no  other  reason 
but  this,  because  thereby  the  two  images  of  the  object 
falling  upon  corresponding  points,  the  eyes  assist  each 
other  in  vision,  and  the  object  is  seen  better  by  both  to- 
gether, than  it  could  be  by  one;  but  when  the  eyes  are 
not  accurately  directed,  the  two  images  of  an  object  fall 
upon  points  that  do  not  correspond,  whereby  the  sight 
of  one  eye  disturbs  the  sight  of  the  other,  and  the  object 
is  seen  more  indistinctly  with  both  eyes  than  it  would  be 
with  one.  Whence  it  is  reasonable  to  conclude,  that 
this  correspondence  of  certain  points  of  the  refines,  is 
prior  to  the  habits  we  acquire  in  vision,  and  consequently 
is  natural  and  original.  We  have  all  acquired  the  habit 
of  directing  our  eyes  always  in  a  particular  manner, 
which  causes  single  vision.  Now,  if  nature  hath  ordained 
that  we  should  have  single  vision  only,  when  our  eyes 
are  thus  directed,  there  is  an  obvious  reason  why  all 
mankind  should  agree  in  the  habit  of  directing  them  in 
this  manner.  But,  if  single  vision  is  the  effect  of  cus- 
tom, any  other  habit  of  directing  the  eyes  would  have 
answered  the  purpose;  and  no  account  can  be  given  why 
this  particular  habit  should  be  so  universal;  and  it  must 
appear  very  strange,  that  no  one  instance  hath  been 
found  of  a  person  who  had  acquired  the  habit  of  seeing 
objects  single  with  both  eyes,  while  they  were  directed  in 
any  other  manner. 

The  judicious  Dr.  Smith,  in  his  excellent  system  of 
optics,  maintains  the  contrary  opinion,  and  offers  some 
reasonings  and  facts  in  proof  of  it.  He  agrees  with 
Bishop  Berkeley  in  attributing  it  entirely  to  custom, 
that  we  see  objects  single  with  two  eyes,  as  well  as  that 


268  THE  PHILOSOPHY  OF  REID.  [Cn.  VI. 

we  see  objects  erect  by  inverted  images.  Having  con- 
sidered Bishop  Berkeley's  reasonings  in  the  nth  section, 
we  shall  now  beg  leave  to  make  some  remarks  on  what 
Dr.  Smith  hath  said  upon  this  subject,  with  the  respect 
due  to  an  author  to  whom  the  world  owes,  not  only  many 
valuable  discoveries  of  his  own,  but  those  of  the  brightest 
mathematical  genius  of  this  age,  which,  with  great  labour, 
he  generously  redeemed  from  oblivion. 

He  observes,  that  the  question,  Why  we  see  objects 
single  with  two  eyes  ?  is  of  the  same  sort  with  this,  Why 
we  hear  sounds  single  with  two  ears  ? — and  that  the 
same  answer  must  serve  both.  The  inference  intended 
to  be  drawn  from  this  observation  is,  that,  as  the  second 
of  these  phsenomena  is  the  effect  of  custom,  so  likewise 
is  the  first. 

Now,  I  humbly  conceive  that  the  questions  are  not  so 
much  of  the  same  sort,  that  the  same  answer  must  serve 
for  both;  and,  moreover,  that  our  hearing  single  with 
two  ears,  is  not  the  effect  of  custom. 

Two  or  more  visible  objects,  although  perfectly  'simi- 
lar, and  seen  at  the  very  same  time,  may  be  distinguished 
by  their  visible  places;  but  two  sounds  perfectly  similar, 
and  heard  at  the  same  time,  cannot  be  distinguished;  for, 
from  the  nature  of  sound,  the  sensations  they  occasion 
must  coalesce  into  one,  and  lose  all  distinction.  If,  there- 
fore, it  is  asked,  Why  we  hear  sounds  single  with  two 
ears  ?  I  answer,  Not  from  custom ;  but  because  two 
sounds  which  are  perfectly  like  and  synchronous,  have 
nothing  by  which  they  can  be  distinguished.  But  will 
this  answer  fit  the  other  question  ?  I  think  not. 

The  object  makes  an  appearance  to  each  eye,  as  the 
sound  makes  an  impression  upon  each  ear:  so  far  the 
two  senses  agree.  But  the  visible  appearances  may  be 
distinguished  by  place,  when  perfectly  like  in  other  re- 
spects; the  sounds  cannot  be  thus  distinguished:  and 
herein  the  two  senses  differ.  Indeed,  if  the  two  appear- 
ances have  the  same  visible  place,  they  are,  in  that  case, 


SEC.  XVII.)  THE  PHILOSOPHY  OF  REID.  269 

as  incapable  of  distinction  as  the  sounds  were,  and  we 
see  the  object  single.  But  when  they  have  not  the  same 
visible  place,  they  are  perfectly  distinguishable,  and  we 
see  the  object  double.  We  see  the  object  single  only, 
when  the  eyes  are  directed  in  one  particular  manner; 
while  there  are  many  other  ways  of  directing  them  within 
the  sphere  of  our  power,  by  which  we  see  the  object 
double. 

Dr.  Smith  justly  attributes  to  custom  that  well-known 
fallacy  in  feeling,  whereby  a  button  pressed  with  •  two 
opposite  sides  of  two  contiguous  fingers  laid  across,  is 
felt  double.  I  agree  with  him,  that  the  cause  of  this 
appearance  is,  that  those  opposite  sides  of  the  fingers  have 
never  been  used  to  feel  the  same  object,  but  two  different 
objects,  at  the  same  time.  And  I  beg  leave  to  add,  that, 
as  custom  produces  this  phenomenon,  so  a  contrary  cus- 
tom destroys  it;  for,  if  a  man  frequently  accustoms  him- 
self to  feel  the  button  with  his  fingers  across,  it  will  at 
last  be  felt  single ;  as  I  have  found  by  experience. 

It  may  be  taken  for  a  general  rule,  that  things  which 
are  produced  by  custom,  may  be  undone  or  changed  by 
disuse,  or  by  a  contrary  custom.  On  the  other  hand,  it 
is  a  strong  argument,  that  an  effect  is  not  owing  to  cus- 
tom, but  to  the  constitution  of  nature,  when  a  contrary 
custom,  long  continued,  is  found  neither  to  change  nor 
weaken  it.  I  take  this  to  be  the  best  rule  by  which  we 
can  determine  the  question  presently  under  consideration. 
I  shall,  therefore,  mention  two  facts  brought  by  Dr. 
Smith,  to  prove  that  the  corresponding  points  of  the 
retina  have  been  changed  by  custom;  and  then  I  shall 
mention  some  facts  tending  to  prove,  that  there  are  cor- 
responding points  of  the  retina  of  the  eyes  originally,  and 
that  custom  produces  no  change  in  them. 

"One  fact  is  related  upon  the  authority  of  Martin 
Folkes,  Esq.,  who  was  informed  by  Dr.  Hepburn  of 
Lynn,  that  the  Rev.  Mr.  Foster  of  Clinch wharton,  in  that 
neighbourhood,  having  been  blind  for  some  years  of  a 


270  THE  PHILOSOPHY  OF  REID.  |CH.  VI. 

gulta  serena,  was  restored  to  sight  by  salivation;  and  that, 
upon  his  first  beginning  to  see,  all  objects  appeared  to 
him  double;  but  afterwards,  the  two  appearances  ap- 
proaching by  degrees,  he  came  at  last  to  see  single,  and 
as  distinctly  as  he  did  before  he  was  blind/' 

Upon  this  case,  I  observe,  First,  That  it  does  not  prove 
any  change  of  the  corresponding  points  of  the  eyes,  un- 
less we  suppose,  what  is  not  affirmed,  that  Mr.  Foster 
directed  his  eyes  to  the  object  at  first,  when  he  saw  double, 
with -the  same  accuracy,  and  in  the  same  manner,  that  he 
did  afterwards,  when  he  saw  single.  Secondly,  If  we 
should  suppose  this,  no  account  can  be  given,  why  at 
first  the  two  appearances  should  be  seen  at  one  certain 
angular  distance  rather  than  another;  or  why  this  angular 
distance  should  gradually  decrease,  until  at  last  the  ap- 
pearances coincided.  How  could  this  effect  be  produced 
by  custom  ?  But,  Thirdly,  Every  circumstance  of  this 
case  may  be  accounted  for  on  the  supposition  that  Mr. 
Foster  had  corresponding  points  in  the  retina  of  his  eyes 
from  the  time  he  began  to  see,  and  that  custom  made  no 
change  with  regard  to  them.  We  need  only  further  sup- 
pose, what  is  common  in  such  cases,  that,  by  some  years' 
blindness,  he  had  lost  the  habit  of  directing  his  eyes  ac- 
curately to  an  object,  and  that  he  gradually  recovered 
this  habit  when  he  came  to  see. 

The  second  fact  mentioned  by  Dr.  Smith,  is  taken  from 
Mr.  Cheselden's  "Anatomy,"  and  is  this: — "A  gentle- 
man who,  from  a  blow  on  the  head,  had  one  eye  dis- 
torted, found  every  object  appear  double;  but,  by  de- 
grees, the  most  familiar  ones  became  single;  and,  in  time, 
all  objects  became  so  without  any  amendment  of  the  dis- 
tortion. " 

I  observe  here,  that  it  is  not  said  that  the  two  appear- 
ances gradually  approached,  and  at  last  united,  without 
any  amendment  of  the  distortion.  This  would  indeed 
have  been  a  decisive  proof  of  a  change  in  the  correspond- 
ing points  of  the  retina,  and  yet  of  such  a  change  as 


SEC.  XVII.)  THE  PHILOSOPHY  OF  REID.  271 

could  not  be  accounted  for  from  custom.  Bu.  this  is 
not  said;  and,  if  it  had  been  observed,  a  circumstance  so 
remarkable  would  have  been  mentioned  by  Mr.  Cheselden, 
as  it  was  in  the  other  case  by  Dr.  Hepburn.  We  may, 
therefore,  take  it  for  granted,  that  one  of  the  appearances 
vanished  by  degrees,  without  approaching  to  the  other. 
And  this  I  conceive  might  happen  several  ways.  First, 
The  sight  of  the  distorted  eye  might  gradually  decay  by 
the  hurt;  so  the  appearances  presented  by  that  eye  would 
gradually  vanish.  Secondly,  A  small  and  unperceived 
change  in  the  manner  of  directing  the  eyes,  might  oc- 
casion his  not  seeing  the  object  with  the  distorted  eye,  as 
appears  from  §  15,  Art.  10.  Thirdly,  By  acquiring  the 
habit  of  directing  one  and  the  same  eye  always  to  the  ob- 
ject, the  faint  and  oblique  appearance  presented  by  the 
other  eye,  might  be  so  little  attended  to  when  it  became 
familiar,  as  not  to  be  perceived.  One  of  these  causes,  or 
more  of  them  concurring,  might  produce  the  effect 
mentioned,  without  any  change  of  the  corresponding 
points  of  the  eyes. 

For  these  reasons,*  the  facts  mentioned  by  Dr.  Smith, 
although  curious,  seem  not  to  be  decisive. 

The  following  facts  ought  to  be  put  in  the  opposite 
scale.  First,  in  the  famous  case  of  the  young  gentleman 
couched  by  Mr.  Cheselden,  after  having  had  cataracts  on 
both  eyes  until  he  was  [above]  thirteen  years  of  age,  it 
appears  that  he  saw  objects  single  from  the  time  he  be- 
gan to  see  with  both  eyes.  Mr.  Cheselden's  words  are, 
"And  now,  being  lately  couched  of  his  other  eye,  he 
says,  that  objects,  at  first,  appeared  large  to  this  eye,  but 
not  so  large  as  they  did  at  first  to  the  other ;  and,  looking 
upon  the  same  object  with  both  eyes,  he  thought  it  looked 
about  twice  as  large  as  with  the  first  couched  eye  only, 
but  not  double,  that  we  can  anywise  discover." 

Secondly,  The  three  young  gentlemen  mentioned  in 
the  last  section,  who  had  squinted,  as  far  as  I  know, 
from  infancy,  as  soon  as  they  learned  to  direct  both  eyes 


272  THE  PHILOSOPHY  OF  REID.  [Cn.  Vl. 

to  an  object,  saw  it  single.  In  these  four  cases,  it  ap- 
pears evident  that  the  centres  of  the  retince  corresponded 
originally,  and  before  custom  could  produce  any  such 
effect ;  for  Mr.  Cheselden's  young  gentleman  had  never 
been  accustomed  to  see  at  all  before  he  was  couched;  and 
the  other  three  had  never  been  accustomed  to  direct  the 
axes  of  both  eyes  to  the  object. 

Thirdly,  from  the  facts  recited  in  §  13,  it  appears, 
that,  from  the  time  we  are  capable  of  observing  the  phae- 
nomena  of  single  and  double  vision,  custom  makes  no 
change  in  them. 

I  have  amused  myself  with  such  observations  for  more 
than  thirty  years ;  and  in  every  case  wherein  I  saw  the 
object  double  at  first,  I  see  it  so  to  this  day,  notwith- 
standing the  constant  experience  of  its  being  single.  In 
other  cases,  where  I  know  there  are  two  objects,  there 
appears  only  one,  after  thousands  of  experiments. 

Let  a  man  look  at  a  familiar  object  through  a  poly- 
hedron, or  multiplying-glass,  every  hour  of  his  life,  the 
number  of  visible  appearances  will  be  the  same  at  last  as 
at  first ;  nor  does  any  number  of  experiments,  or  length 
of  time,  make  the  least  change. 

Effects  produced  by  habit,  must  vary  according  as  the 
acts  by  which  the  habit  is  acquired  are  more  or  less  fre- 
quent; but  the  phaenomena  of  single  and  double  vision 
are  so  invariable  and  uniform  in  all  men,  are  so  exactly 
regulated  by  mathematical  rules,  that  I  think  we  have 
good  reason  to  conclude  that  they  are  not  the  effect  of 
custom,  but  of  fixed  and  immutable  laws  of  nature. 

Section  XVIII. 
OF  DR.  PORTERFIELD'S  ACCOUNT  OF  SINGLE  AND  DOUBLE  VISION. 

Bishop  Berkeley  and  Dr.  Smith  seem  to  attribute  too 
1  much  to  custom  in  vision,  Dr.  Porterfield  too  little. 
This  ingenious  writer  thinks,  that,  by  an  original  law 


SEC.  XVIII.]  THE  PHILOSOPHY  OF  REID.  273 

of  our  nature,  antecedent  to  custom  and  experience,  we 
perceive  visible  objects  in  their  true  place,  not  only  as  to 
their  direction,  but  likewise  as  to  their  distance  from  the 
eye;  and,  therefore,  he  accounts  for  our  seeing  objects 
single,  with  two  eyes,  in  this  manner.  Having  the 
faculty  of  perceiving  the  object  with  each  eye  in  its 
true  place,  we  must  perceive  it  with  both  eyes  in  the 
same  place ;  and,  consequently,  must  perceive  it  sin- 
gle. 

He  is  aware  that  this  principle,  although  it  accounts 
for  our  seeing  objects  single  with  two  eyes,  yet  does  not 
at  all  account  for  our  seeing  objects  double  ;  and,  where- 
as other  writers  on  this  subject  take  it  to  be  a  sufficient 
cause  for  double  vision  that  we  have  two  eyes,  and  only 
find  it  difficult  to  assign  a  cause  for  single  vision,  on  the 
contrary,  Dr.  Porterfield's  principle  throws  all  the  diffi- 
culty on  the  other  side. 

Therefore,  in  order  to  account  for  the  phenomena  of 
double  vision,  he  advances  another  principle,  without 
signifying  whether  he  conceives  it  to  be  an  original  law 
of  our  nature,  or  the  effect  of  custom.  It  is,  That  our 
natural  perception  of  the  distance  of  objects  from  the  eye, 
is  not  extended  to  all  the  objects  that  fall  within  the  field 
of  vision,  but  limited  to  that  which  we  directly  look  at ; 
and  that  the  circumjacent  objects,  whatever  be  their  real 
distance,  are  seen  at  the  same  distance  with  the  object 
we  look  at ;  as  if  they  were  all  in  the  surface  of  a  sphere, 
whereof  the  eye  is  the  centre. 

Thus,  single  vision  is  accounted  for  by  our  seeing  the 
true  distance  of  an  object  which  we  look  at ;  and  double 
vision,  by  a  false  appearance  of  distance  in  objects  which 
we  do  not  directly  look  at. 

We  agree  with  this  learned  and  ingenious  author,  that 
it  is  by  a  natural  and  original  principle  that  we  see  vis- 
ible objects  in  a  certain  direction  from  the  eye,  and 
honour  him  as  the  author  of  this  discovery:  but  we  can- 
not assent  to  either  of  those  principles  by  which  he  ex- 


274  THE  PHILOSOPHY  OF  REID.  [Cn.  VI. 

plains  single  and  double  vision — for  the  following  rea- 
sons:— 

1.  Our  having  a  natural  and  original  perception  of 
the  distance  of  objects  from  the  eye,  appears  contrary  to 
a  well-attested  fact:  for  the  young  gentleman  couched  by 
Mr.   Cheselden  imagined,  at  first,  that  whatever  he  saw 
touched  his  eye,  as  what  he  felt  touched  his  hand. 

2.  The  perception  we  have  of  the  distance  of  objects 
from  the  eye,  whether  it  be  from  nature  or  custom,  is 
not  so  accurate  and  determined  as  is  necessary  to  pro- 
duce single  vision.     A  mistake  of  the  twentieth  or  thir- 
tieth part  of  the  distance  of  a  small  object,  such  as  a  pin, 
ought,  according  to  Dr.  Porterfield's  hypothesis,  to  make 
it  appear  double.     Very  few  can  judge  of  the  distance  of 
a  visible  object  with  such  accuracy.     Yet  we  never  find 
double  vision  produced  by  mistaking  the  distance  of  the 
object.     There  are  many  cases  in  vision,  even  with  the 
naked  eye,  wherein  we  mistake  the  distance  of  an  object 
by  one  half  or  more:  why  do  we  see  such  objects  single  ? 
When  I  move   my  spectacles  from  my  eyes  toward  a 
small  object,  two  or  three  feet  distant,  the  object  seems 
to  approach,  so  as  to  be  seen  at  last  at  about  half  its  real 
distance;  but  it  is  seen  single  at  that  apparent  distance, 
as  well  as  when  we  see  it  with  the  naked  eye  at  its  real 
distance.     And  when  we  look  at  an  object  with  a  binoc- 
ular telescope,  properly  fitted  to  the  eyes,  we  see  it  sin- 
gle, while  it  appears  fifteen  or  twenty  times  nearer  than 
it  is.     There  are  then  few  cases  wherein  the  distance  of 
an  object  from  the  eye  is  seen  so  accurately  as  is  neces- 
sary for  single  vision,  upon  this  hypothesis:  this  seems 
to  be  a  conclusive  argument  against  the  account  given 
of  single  vision.     We  find,  likewise,  that  false  judgments 
or  fallacious  appearances  of  the  distance  of  an  object,  do 
not  produce  double  vision:  this  seems  to  be  a  conclusive 
argument  against  the  account  given  of  double  vision. 

3.  The  perception  we  have  of  the  linear  distance  of 
objects   seems  to   be  wholly  the  effect  of  experience. 


SEC.  XVIII.]  THE  PHILOSOPHY  OF  REID.  275 

This,  I  think,  hath  been  proved  by  Bishop  Berkeley 
and  by  Dr.  Smith ;  and  when  we  come  to  point  out 
the  means  of  judging  of  distance  by  sight,  it  will  appear 
that  they  are  all  furnished  by  experience. 

4.  Supposing  that,  by  a  law  of  our  nature,  the  distance 
of  objects  from  the  eye  were  perceived  most  accurately,  as 
well  as  their  direction,  it  will  not  follow  that  we  must 
see  the  object  single.     Let  us  consider  what  means  such 
a  law  of  nature  would  furnish  for  resolving  the  question, 
Whether  the  objects  of  the  two  eyes  are  in  one  and  the 
same  place,  and  consequently  are  not  two,  but  one  ? 

Suppose  then,  two  right  lines,  one  drawn  from  the  centre 
of  one  eye  to  its  object,  the  other  drawn,  in  like  man- 
ner, from  the  centre  of  the  other  eye  to  its  object.  This 
law  of  nature  gives  us  the  direction  or  position  of  each 
of  these  right  lines,  and  the  length  of  each  ;  and  this  is 
all  that  it  gives.  These  are  geometrical  data,  and  we 
may  learn  from  geometry  what  is  determined  by  their 
means.  Is  it,  then,  determined  by  these  da/a,  Whether 
the  two  right  lines  terminate  in  one  and  the  same  point, 
or  not  ?  No,  truly.  In  order  to  determine  this,  we 
must  have  three  other  data.  We  must  know  whether  the 
two  right  lines  are  in  one  plane ;  we  must  know  what 
angle  they  make ;  and  we  must  know  the  distance  be. 
tween  the  centres  of  the  eyes.  And  when  these  things 
are  known,  we  must  apply  the  rules  of  trigonometry,  be- 
fore we  can  resolve  the  question,  Whether  the  objects  of 
the  two  eyes  are  in  one  and  the  same  place;  and,  conse- 
quently, whether  they  are  two  or  one  ? 

5.  That  false  appearance  of  distance  into  which  double 
vision  is  resolved,  cannot  be  the  effect  of  custom,  for 
constant  experience  contradicts  it.     Neither  hath  it  the 
features  of  a  law  of  nature,  because  it  does  not  answer 
any  good  purpose,  nor,  indeed,  any  purpose  at  all,  but 
to  deceive  us.     But  why  should  we  seek  for  arguments, 
in  a  question  concerning  what  appears  to  us,  or  does  not 
appear  ?     The  question  is,  At  what  distance  do  the  ob- 


276  THE  PHILOSOPHY  OF  REID.  [Cn.  VI. 

jects  now  in  my  eye  appear  ?  Do  they  all  appear  at  one 
distance,  as  if  placed  in  the  concave  surface  of  a  sphere, 
the  eye  being  in  the  centre  ?  Every  man,  surely,  may 
know  this  with  certainty ;  and,  if  he  will  but  give  atten- 
tion to  the  testimony  of  his  eyes,  needs  not  ask  a  philoso- 
pher how  visible  objects  appear  to  him.  Now,  it  is  very 
true,  that,  if  I  look  up  to  a  star  in  the  heavens,  the  other 
stars  that  appear  at  the  same  time,  do  appear  in  this  man- 
ner: yet  this  phaenomenon  does  not  favour  Dr.  Porter- 
field's  hypothesis ;  for  the  stars  and  heavenly  bodies  do 
not  appear  at  their  true  distances  when  we  look  directly 
to  them,  any  more  than  when  they  are  seen  obliquely  : 
and  if  this  phaenomenon  be  an  argument  for  Dr.  Porter- 
field's  second  principle,  it  must  destroy  the  first  I 

The  true  cause  of  this  phaenomenon  will  be  given  after- 
wards ;  therefore,  setting  it  aside  for  the  present,  let  us 
put  another  case.  I  sit  in  my  room,  and  direct  my 
eyes  to  the  door,  which  appears  to  be  about  sixteen  feet 
distant :  at  the  same  time,  I  see  many  other  objects 
faintly  and  obliquely — the  floor,  floor-cloth,  the  table 
which  I  write  upon,  papers,  standish,  candle,  &c.  Now, 
do  all  these  objects  appear  at  the  same  distance  of  six- 
teen feet  ?  Upon  the  closest  attention  I  find  they  do 
not 

Section  XIX. 

OF  DR  BRIGGS'S  THEORY  AND  SIR  ISAAC  NEWTON'S  CONJECTURE 
ON   THIS    SUBJECT. 

I  am  afraid  the  reader,  as  well  as  the  writer,  is  already 
tired  of  the  subject  of  single  and  double  vision.  The 
multitude  of  theories  advanced  by  authors  of  great  name, 
and  the  multitude  of  facts,  observed  without  sufficient 
skill  in  optics,  or  related  without  attention  to  the  most 
material  and  decisive  circumstances,  have  equally  con- 
tributed to  perplex  it  ' 


SEC.XVIIL]  THE  PHILOSOPHY  OF  REID.  277 


In  order  to  bring  it  to  some  issue,  I  have,  in  the 
section,  given  a  more  full  and  regular  deduction  than 
had  been  given  heretofore,  of  the  phaenomena  of  single 
and  double  vision,  in  those  whose  sight  is  perfect  ;  and 
have  traced  them  up  to  one  general  principle,  which  ap- 
pears to  be  a  law  of  vision  in  human  eyes  that  are  perfect 
and  in  their  natural  state. 

In  the  1  4th  section,  I  have  made  it  appear,  that  this 
law  of  vision,  although  excellently  adapted  to  the  fab- 
ric of  human  eyes,  cannot  answer  the  purposes  of  vision 
in  some  other  animals  ;  and  therefore,  very  probably  is 
not  common  to  all  animals.  The  purpose  of  the  i5th 
and  1  6th  sections  is,  to  inquire,  Whether  there  be  any 
deviation  from  this  law  of  vision  in  those  who  squint  ?  — 
a  question  which  is  of  real  importance  in  the  medical  art, 
as  well  as  in  the  philosophy  of  vision  ;  but  which,  after 
all  that  hath  been  observed  and  written  on  the  subject, 
seems  not  to  be  ripe  for  a  determination,  for  want  of  prop- 
er observations.  Those  who  have  had  skill  to  make 
proper  observations,  have  wanted  opportunities  ;  and 
those  who  have  had  opportunities,  have  wanted  skill  or 
attention.  I  have  therefore  thought  it  worth  while  to 
give  a  distinct  account  of  the  observations  necessary  for 
the  determination  of  this  question,  and  what  conclusions 
may  be  drawn  from  the  facts  observed.  I  have  likewise 
collected,  and  set  in  one  view,  the  most  conclusive  facts 
that  have  occurred  in  authors,  or  have  fallen  under  my 
own  observation. 

It  must  be  confessed  that  these  facts,  when  applied  to 
the  question  in  hand,  make  a  very  poor  figure  ;  and  the 
gentlemen  of  the  medical  faculty  are  called  upon,  for  the 
honour  of  their  profession,  and  for  the  benefit  of  man- 
kind, to  add  to  them. 

All  the  medical,  and  all  the  optical  writers  upon  the 
strabismus  that  I  have  met  with,  except  Dr.  Jurin,  either 
affirm,  or  take  it  for  granted,  that  squinting  persons  see 
the  object  with  both  eyes,  and  yet  see  it  single.  Dr. 


278  THE  PHILOSOPHY  OF  REID.  [Cn.  VI. 

Jurin  affirms  that  squinting  persons  never  see  the  object 
with  both  eyes  ;  and  that,  if  they  did,  they  would  see 
it  double.  If  the  common  opinion  be  true,  the  cure  of 
a  squint  would  be  as  pernicious  to  the  sight  of  the  patient, 
as  the  causing  of  a  permanent  squint  would  be  to  one 
who  naturally  had  no  squint;  and  therefore,  no  physician 
ought  to  attempt  such  a  cure,  no  patient  ought  to  sub- 
mit to  it.  But,  if  Dr.  Jurin's  opinion  be  true,  most 
young  people  that  squint  may  cure  themselves,  by  tak- 
ing some  pains  ;  and  may  not  only  remove  the  deform- 
ity, but,  at  the  same  time,  improve  their  sight.  If  the 
common  opinion  be  true,  the  centres,  and  other  points 
of  the  two  retince,  in  squinting  persons,  do  not  corre- 
spond, as  in  other  men,  and  Nature,  in  them,  deviates 
from  her  common  rule.  But,  if  Dr.  Jurin's  opinion  be 
true,  there  is  reason  to  think  that  the  same  general  law 
of  vision,  which  we  have  found  in  perfect  human  eyes,  ex- 
tends also  to  those  which  squint. 

It  is  impossible  to  determine,  by  reasoning,  which  of 
these  opinions  is  true  ;  or  whether  one  may  not  be  found 
true  in  same  patients,  and  the  other  in  others.  Here, 
experience  and  observation  are  our  only  guides  ;  and  a  de- 
duction of  instances  is  the  only  rational  argument.  It 
might,  therefore,  have  been  expected,  that  the  patrons  of 
the  contrary  opinions  should  have  given  instances  in  sup- 
port of  them  that  are  clear  and  indisputable  ;  but  I  have 
not  found  one  such  instance  on  either  side  of  the  ques- 
tion, in  all  the  authors  I  have  met  with.  I  have  given 
three  instances  from  my  own  observation,  in  confirmation 
of  Dr.  Jurin's  opinion,  which  admit  of  no  doubt ;  and 
one  which  leans  rather  to  the  other  opinion,  but  is  du- 
bious. And  here  I  must  leave  the  matter  to  further  ob- 
servation. 

In  the  iyth  section,  I  have  endeavoured  to  shew  that 
the  correspondence  and  [or]  sympathy  of  certain  points 
of  the  two  retina,  into  which  we  have  resolved  all  the 
phaenomena  of  single  and  double  vision,  is  not,  as  Dr. 


SEC.  XIX.]  THE  PHILOSOPHY  OF  REID.  279 

Smith  conceived,  the  effect  of  custom,  nor  can  [it]  be 
changed  by  custom,  but  is  a  natural  and  original  prop- 
erty of  human  eyes;  and,  in  the  last  section,  that  it  is 
not  owing  to  an  original  and  natural  perception  of  the 
true  distance  of  objects  from  the  eye,  as  Dr.  Porterfield 
imagined.  After  this  recapitulation,  which  is  intended 
to  relieve  the  attention  of  the  reader,  shall  we  enter  into 
more  theories  upon  this  subject  ? 

That  of  Dr.  Briggs — first  published  in  English,  in  the 
"Philosophical  Transactions,"  afterwards  in  Latin, 
under  the  title  of  "  Nova  Visionis  Theoria,"  with  a  pref- 
atory epistle  of  Sir  Isaac  Newton  to  the  author — amounts 
to  this,  That  the  fibres  of  the  optic  nerves,  passing  from 
corresponding  points  of  the  retina 'to  the  thalami nervorum 
opticorum,  having  the  same  length,  the  same  tension,  and 
a  similar  situation,  will  have  the  same  tone;  and,  there- 
fore, their  vibrations,  excited  by  the  impression  of  the 
rays  of  light,  will  be  like  unisons  in  music,  and  will  pre- 
sent one  and  the  same  image  to  the  mind:  but  the  fibres 
passing  from  parts  of  the  retina  which  do  not  correspond, 
having  different  tensions  and  tones,  will  have  discordant 
vibrations;  and,  therefore,  present  different  images  to  the 
mind. 

I  shall  not  enter  upon  a  particular  examination  of  this 
theory.  It  is  enough  to  observe,  in  general,  that  it  is  a 
system  of  conjectures  concerning  things  of  which  we  are 
entirely  ignorant;  and  that  all  such  theories  in  philosophy 
deserve  rather  to  be  laughed  at,  than  to  be  seriously 
refuted. 

From  the  first  dawn  of  philosophy  to  this  day,  it  hath 
been  believed  that  the  optic  nerves  are  intended  to  carry 
the  images  of  visible  objects  from  the  bottom  of  the  eye  to 
the  mind;  and  that  the  nerves  belonging  to  the  organs  of 
the  other  senses  have  a  like  office.  But  how  do  we  know 
this  ?  We  conjecture  it;  and,  taking  this  conjecture  for 
a  truth,  we  consider  how  the  nerves  may  best  answer  this 
purpose.  The  system  of  the  nerves,  for  many  ages,  was 


280  THE   PHILOSOPHY   OF  REID.  [Cn.  VI. 

taken  to  be  a  hydraulic  engine,  consisting  of  a  bundle  of 
pipes,  which  carried  to  and  fro  a  liquor  called  animal 
spirits.  About  the  time  of  Dr.  Briggs,  it  was  thought 
rather  to  be  a  stringed  instrument,  composed  of  vibrat- 
ing chords,  each  of  which  had  its  proper  tension  and 
tone.  But  some,  with  as  great  probability,  conceived  it 
to  be  a  wind  instrument,  which  played  its  part  by  the 
vibrations  of  an  elastic  aether  in  the  nervous  fibrils. 

These,  I  think,  are  all  the  engines  into  which  the  nerv- 
ous system  hath  been  moulded  by  philosophers,  for 
conveying  the  images  of  sensible  things  from  the  organ 
to  the  sensorium.  And,  for  all  that  we  know  of  the  mat- 
ter, every  man  may  freely  choose  which  he  thinks  fittest 
for  the  purpose;  for,  from  fact  and  experiment,  no  one 
of  them  can  claim  preference  to  another.  Indeed,  they 
all  seem  so  unhandy  engines  for  carrying  images,  that  a 
man  would  be  tempted  to  invent  a  new  one. 

Since,  therefore,  a  blind  man  may  guess  as  well  in  the 
dark  as  one  that  sees,  I  beg  leave  to  offer  another  con- 
jecture touching  the  nervous  system,  which,  I  hope,  will 
answer  the  purpose  as  well  as  those  we  have  mentioned, 
and  which  recommends  itself  by  its  simplicity.  Why 
may  not  the  optic  nerves,  for  instance,  be  made  up  of 
empty  tubes,  opening  their  mouths  wide  enough  to  re- 
ceive the  rays  of  light  which  form  the  image  upon  the 
retina,  and  gently  conveying  them  safe,  and  in  their  prop- 
er order,  to  the  very  seat  of  the  soul,  until  they  flash  in 
her  face  ?  It  is  easy  for  an  ingenious  philosopher  to  fit 
the  caliber  of  these  empty  tubes  to  the  diameter  of  the 
particles  of  light,  so  as  they  shall  receive  no  grosser  kind 
of  matter;  and,  if  these  rays  should  be  in  danger  of 
mistaking  their  way,  an  expedient  may  also  be  found  to 
prevent  this;  for  it  requires  no  more  than  to  bestow  upon 
the  tubes  of  the  nervous  system  a  peristaltic  motion,  like 
that  of  the  alimentary  tube. 

It  is  a  peculiar  advantage  of  this  hypothesis,    that, 
although    all    philosophers  believe  that  the  species  or 


SEC.  XIX.]  THE  PHILOSOPHY  OF  REID.  28 1 

images  of  things  are  conveyed  by  the  nerves  to  the  soul, 
yet  none  of  their  hypotheses  shew  how  this  may  be  done. 
For  how  can  the  images  of  sound,  taste,  smell,  colour, 
figure,  and  all  sensible  qualities,  be  made  out  of  the 
vibrations  of  musical  chords,  or  the  undulations  of 
animal  spirits,  or  of  aether  ?  We  ought  not  to  suppose 
means  inadequate  to  the  end.  Is  it  not  as  philosophi 
cal,  and  more  intelligible,  to  conceive,  that,  as  the 
stomach  receives  its  food,  so  the  soul  receives  her  images 
by  a  kind  of  nervous  deglutition  ?  I  might  add,  that  we 
need  only  continue  this  peristaltic  motion  of  the  nervous 
tubes  from  the  sensorium  to  the  extremities  of  the  nerves 
that  serve  the  muscles,  in  order  to  account  for  muscular 
motion. 

Thus  Nature  will  be  consonant  to  herself:  and,  as  sen- 
sation will  be  the  conveyance  of  the  ideal  aliment  to  the 
mind,  so  muscular  motion  will  be  the  expulsion  of  the 
recrementitious  part  of  it.  For  who  can  deny,  that  the 
images  of  things  conveyed  by  sensation,  may,  after  due 
concoction,  become  fit  to  be  thrown  off  by  muscular 
motion  ?  I  only  give  hints  of  these  things  to  the  ingen- 
ious, hoping  that  in  time  this  hypothesis  may  be  wrought 
up  into  a  system  as  truly  philosophical  as  that  of  animal 
spirits,  or  the  vibration  of  nervous  fibres. 

To  be  serious:  In  the  operations  of  nature,  I  hold  the 
theories  of  a  philosopher,  which  are  unsupported  by  fact, 
in  the  same  estimation  with  the  dreams  of  a  man  asleep, 
or  the  ravings  of  a  madman.  We  laugh  at  the  Indian 
philosopher,  who,  to  account  for  the  support  of  the  earth, 
contrived  the  hypothesis  of  a  huge  elephant,  and,  to  sup- 
port the  elephant,  a  huge  tortoise.  If  we  will  candidly 
confess  the  truth,  we  know  as  little  of  the  operation  of 
the  nerves,  as  he  did  of  the  manner  in  which  the  earth 
is  supported;  and  our  hypotheses  about  animal  spirits,  or 
about  the  tension  and  vibrations  of  the  nerves,  are  as 
like  to  be  true,  as  his  about  the  support  of  the  earth. 
His  elephant  was  a  hypothesis,  and  our  hypotheses  are 


282  THE   PHILOSOPHY   OF  REID.  (Cn.  VI. 

elephants.  Every  theory  in  philosophy,  which  is  built 
on  pure  conjecture,  is  an  elephant ;  and  every  theory 
that  is  supported  partly  by  fact,  and  partly  by  conject- 
ure, is  like  Nebuchadnezzar's  image,  whose  feet  were 
partly  of  iron  and  partly  of  clay. 

The  great  Newton  first  gave  an  example  to  philoso- 
phers, which  always  ought  to  be,  but  rarely  hath  been 
followed,  by  distinguishing  his  conjectures  from  his  con- 
clusions, and  putting  the  former  by  themselves,  in  the 
modest  form  of  queries.  This  is  fair  and  legal;  but  all 
other  philosophical  traffic  in  conjecture  ought  to  be  held 
contraband  and  illicit.  Indeed,  his  conjectures  have 
commonly  more  foundation  in  fact,  and  more  verisimili- 
tude, than  the  dogmatical  theories  of  most  other  philos- 
ophers; and,  therefore,  we  ought  not  to  omit  that  which 
he  hath  offered  concerning  the  cause  of  our  seeing  ob- 
jects single  with  two  eyes,  in  the  1 5th  query  annexed  to 
his  "Optics." 

"Are  not  the  species  of  objects  seen  with  both  eyes, 
united  where  the  optic  nerves  meet  before  they  come 
into  the  brain,  the  fibres  on  the  right  side  of  both  nerves 
uniting  there,  and  after  union  going  thence  into  the 
brain  in  the  nerve  which  is  on  the  right  side  of  the  head, 
and  the  fibres  on  the  left  side  of  both  nerves  uniting  in 
the  same  place,  and  after  union  going  into  the  brain  in 
the  nerve  which  is  on  the  left  side  of  the  head,  and  these 
two  nerves  meeting  in  the  brain  in  such  a  manner  that 
their  fibres  make  but  one  entire  species  or  picture,  half 
of  which  on  the  right  side  of  the  sensorium  comes  from 
the  right  side  of  both  eyes  through  the  right  side  of  both 
optic  nerves,  to  the  place  where  the  nerves  meet,  and 
from  thence  on  the  right  side  of  the  head  into  the  brain, 
and  the  other  half  on  the  left  side  of  the  sensorium  comes, 
in  like  manner,  from  the  left  side  of  both  eyes  ?  For  the 
optic  nerves  of  such  animals  as  look  the  same  way  with 
both  eyes  (as  men.  dogs,  sheep,  oxen,  &c.)  meet  before 
they  come  into  the  brain;  but  the  optic  nerves  of  such 


SEC.  XIX.]  THE  PHILOSOPHY  OF  REID.  283 

animals  as  do  not  look  the  same  way  with  both  eyes  (as 
of  fishes,  and  of  the  chameleon)  do  not  meet,  if  I  am 
rightly  informed." 

I  beg  leave  to  distinguish  this  query  into  two,  which 
are  of  very  different  natures;  one  being  purely  anatomi- 
cal, the  other  relating  to  the  carrying  species  or  pictures 
of  visible  objects  to  the  sensorium. 

The  first  question  is,  Whether  the  fibres  coming  from 
corresponding  points  of  the  two  refines  do  not  unite  at 
the  place  where  the  optic  nerves  meet,  and  continue 
united  from  thence  to  the  brain;  so  that  the  right  optic 
nerve,  after  the  meeting  of  the  two  nerves,  is  composed 
of  the  fibres  coming  from  the  right  side  of  both  retince, 
and  the  left,  of  the  fibres  coming  from  the  left  side  of 
both  retina? 

This  is  undoubtedly  a  curious  and  rational  question  ; 
because,  if  we  could  find  ground  from  anatomy  to 
answer  it  in  the  affirmative,  it  would  lead  us  a  step 
forward  in  discovering  the  cause  of  the  correspondence 
and  sympathy  which  there  is  between  certain  points  of 
the  two  retina.  For,  although  we  know  not  what  is  the 
particular  function  of  the  optic  nerves,  yet  it  is  probable 
that  some  impression  made  upon  them,  and  communi- 
cated along  their  fibres,  is  necessary  to  vision;  and, 
whatever  be  the  nature  of  this  impression,  if  two  fibres 
are  united  into  one,  an  impression  made  upon  one  of 
them,  or  upon  both,  may  probably  produce  the  same 
effect.  Anatomists  think  it  a  sufficient  account  of  a 
sympathy  between  two  parts  of  the  body,  when  they  are 
served  by  branches  of  the  same  nerve;  we  should,  there- 
fore, look  upon  it  as  an  important  discovery  in  anatomy, 
if  it  were  found  that  the  same  nerve  sent  branches  to  the 
corresponding  points  of  the  refines. 

But  hath  any  such  discovery  been  made  ?  No,  not  so 
much  as  in  one  subject,  as  far  as  I  can  learn;  but,  in 
several  subjects,  the  contrary  seems  to  have  been  dis- 
covered. Dr.  Porterfield  hath  given  us  two  cases  at 


2&J.  THE  PHILOSOPHY  OF  REID.  [Cn.Vl. 

length  from  Vesalius,  and  one  from  Caesalpinus,  wherein 
the  optic  nerves,  after  touching  one  another  as  usual, 
appeared  to  be  reflected  back  to  the  same  side  whence 
they  came,  without  any  mixture  of  their  fibres.  Each  of 
these  persons  had  lost  an  eye  some  time  before  his  death, 
and  the  optic  nerve  belonging  to  that  eye  was  shrunk, 
so  that  it  could  be  distinguished  from  the  other  at  the 
place  where  they  met.  Another  case,  which  the  same 
author  gives  from  Vesalius,  is  still  more  remarkable;  for 
in  it  the  optic  nerves  did  not  touch  at  all;  and  yet,  upon 
inquiry,  those  who  were  most  familiar  with  the  person  in 
his  lifetime,  declared  that  he  never  complained  of  any 
defect  of  sight,  or  of  his  seeing  objects  double.  Diemer- 
broeck  tells  us,  that  Aquapendens  [abAquapendente]  and 
Valverda  likewise  affirm,  that  they  have  met  with  sub- 
jects wherein  the  optic  nerves  did  not  touch. 

As  these  observations  were  made  before  Sir  Isaac  New- 
ton put  this  query,  it  is  uncertain  whether  he  was 
ignorant  of  them,  or  whether  he  suspected  some  inaccu- 
racy in  them,  and  desired  that  the  matter  might  be  more 
carefully  examined.  But,  from  the  following  passage  of 
the  most  accurate  Winslow,  it  does  not  appear  that  later 
observations  have  been  more  favorable -to  his  conjecture. 
"The  union  of  these  (optic)  nerves,  by  the  small  curva- 
tures of  their  cornua,  is  very  difficult  to  be  unfolded  in 
human  bodies.  This  union  is  commonly  found  to  be 
very  close  ;  but,  in  some  subjects,  it  seems  to  be  no  more 
than  a  strong  adhesion — in  others,  to  be  partly  made  by 
an  intersection  or  crossing  of  fibres.  They  have  been 
found  quite  separate  ;  and,  in  other  subjects,  one  of  them 
has  been  found  to  be  very  much  altered  both  in  size  and 
colour  through  its  whole  passage,  the  other  remaining  in 
its  natural  state." 

When  we  consider  this  conjecture  of  Sir  Isaac  Newton 
by  itself,  it  appears  more  ingenious,  and  to  have  more 
verisimilitude,  than  anything  that  has  been  offered  upon 
the  subject ;  and  we  admire  the  caution  and  modesty  of 


SEC.  XIX.]  THE  PHILOSOPHY  OF  REID.  285 

the  author,  in  proposing  it  only  as  a  subject  of  inquiry: 
but  when  we  compare  it  with  the  observations  of  anato- 
mists which  contradict  it,  we  are  naturally  led  to  this 
reflection,  That,  if  we  trust  to  the  conjectures  of  men  of 
the  greatest  genius  in  the  operations  of  nature,  we  have 
only  the  chance  of  going  wrong  in  an  ingenious  manner. 

The  second  part  of  the  query  is,  Whether  the  two 
species  of  objects  from  the  two  eyes  are  not,  at  the  place 
where  the  optic  nerves  meet,  united  into  one  species  or 
picture,  half  of  which  is  carried  thence  to  the  sensorium 
in  the  right  optic  nerve,  and  the  other  half  in  the  left  ? 
and  whether  these  two  halves  are  not  so  put  together 
again  at  the  sensorium,  as  to  make  one  species  or 
picture  ? 

Here  it  seems  natural  to  put  the  previous  question, 
What  reason  have  we  to  believe  that  pictures  of  objects 
are  at  all  carried  to  the  sensorium,  either  by  the  optic 
nerves,  or  by  any  other  nerves  ?  Is  it  not  possible  that 
this  great  philosopher,  as  well  as  many  of  a  lower  form, 
having  been  led  into  this  opinion  at  first  by  education, 
may  have  continued  in  it,  because  he  never  thought  of 
calling  it  in  question  ?  I  confess  this  was  my  own  case 
for  a  considerable  part  of  my  life.  But  since  I  was  led 
by  accident  to  think  seriously  what  reason  I  had  to  believe 
it,  I  could  find  none  at  all.  It  seems  to  be  a  mere 
hypothesis,  as  much  as  the  Indian  philosopher's  elephant. 
I  am  not  conscious  of  any  pictures  of  external  objects  in 
my  sensorinm,  any  more  than  in  my  stomach  :  the  things 
which  I  perceive  by  my  senses,  appear  to  be  external, 
and  not  in  any  part  of  the  brain;  and  my  sensations, 
properly  so  called,  have  no  resemblance  of  external 
objects. 

The  conclusion  from  all  that  hath  been  said,  in  no  less 
than  seven  sections,  upon  our  seeing  objects  single  with 
two  eyes,  is  this — That,  by  an  original  property  of  human 
eyes,  objects  painted  upon  the  centres  of  the  two  retina, 
or  upon  points  similarly  situate  with  rej 


286  THE  PHILOSOPHY  OF  REID.  [Cn.  VI. 

appear  in  the  same  visible  place;  that  the  most  plausible 
attempts  to  account  for  this  property  of  the  eyes,  have 
been  unsuccessful;  and,  therefore,  that  it  must  be  either 
a  primary  law  of  our  constitution,  or  the  consequence  of 
some  more  general  law,  which  is  not  yet  discovered. 

We  have  now  finished  what  we  intended  to  say,  both 
of  the  visible  appearances  of  things  to  the  eye,  and  of  the 
laws  of  our  constitution  by  which  those  appearances  are 
exhibited.  But  it  was  observed,  in  the  beginning  of  this 
chapter,  that  the  visible  appearances  of  objects  serve  only 
as  signs  of  their  distance,  magnitude,  figure,  and  other 
tangible  qualities.  The  visible  appearance  is  that  which 
is  presented  to  the  mind  by  nature,  according  to  those 
laws  of  our  constitution  which  have  been  explained.  But 
the  thing  signified  by  that  appearance,  is  that  which  is 
presented  to  the  mind  by  custom. 

When  one  speaks  to  us  in  a  language  that  is  familiar, 
we  hear  certain  sounds,  and  this  is  all  the  effect  that  his 
discourse  has  upon  us  by  nature;  but  by  custom  we 
understand  the  meaning  of  these  sounds;  and,  therefore, 
we  fix  our  attention,  not  upon  the  sounds,  but  upon  the 
things  signified  by  them.  In  like  manner,  we  see  only 
the  visible  appearance  of  objects  by  nature;  but  we  learn, 
by  custom  to  interpret  these  appearances,  and  to  under- 
stand their  meaning.  And  when  this  visual  language  is 
learned,  and  becomes  familiar,  we  attend  only  to  the 
things  signified  ;  and  cannot,  without  great  difficulty, 
attend  to  the  signs  by  which  they  are  presented.  The 
mind  passes  from  one  to  the  other  so  rapidly  and  so 
familiarly,  that  no  trace  of  the  sign  is  left  in  the  memory, 
and  we  seem  immediately,  and  without  the  intervention 
of  any  sign,  to  perceive  the  thing  signified. 

When  I  look  at  the  apple-tree  which  stands  before  my 
window,  I  perceive,  at  the  first  glance,  its  distance  and 
magnitude,  the  roughness  of  its  trunk,  the  disposition  of 
its  branches,  the  figure  of  its  leaves  and  fruit.  I  seem  to 
perceive  all  these  things  immediately.  The  visible  ap- 


SEC.  XX.]  THE  PHILOSOPHY  OP  REID.  287 

pearance  which  presented  them  all  to  the  mind,  has 
entirely  escaped  me  ;  I  cannot,  without  great  difficulty, 
and  painful  abstraction,  attend  to  it,  even  when  it  stands 
before  me.  Yet  it  is  certain  that  this  visible  appearance 
only  is  presented  to  my  eye  by  nature,  and  that  I  learned 
by  custom  to  collect  all  the  rest  from  it.  If  I  had  never 
seen  before  now,  I  should  not  perceive  either  the  distance 
or  tangible  figure  of  the  tree;  and  it  would  have  required 
the  practice  of  seeing  for  many  months,  to  change  that 
original  perception  which  nature  gave  me  by  my  eyes, 
into  that  which  I  now  have  by  custom. 

The  objects  which  we  see  naturally  and  originally,  as 
hath  been  before  observed,  have  length  and  breadth,  but 
no  thickness  nor  distance  from  the  eye.  Custom,  by  a 
kind  of  legerdemain,  withdraws  gradually  these  original 
and  proper  objects  of  sight,  and  substitutes  in  their  place 
objects  of  touch,  which  have  length,  breadth,  and  thick- 
ness, and  a  determinate  distance  from  the  eye.  By  what 
means  this  change  is  brought  about,  and  what  principles 
of  the  human  mind  concur  in  it,  we  are  next  to  inquire. 


Section  XX. 

OF   PERCEPTION    IN    GENERAL. 

Sensation,  and  the  perception  *  of  external  objects  by 
the  senses,  though  very  different  in  their  nature,  have 
commonly  been  considered  as  one  and  the  same  thing,  f 

*  On  the  distinction  of  Sensation  proper,  from  Perception  proper, 
see  "  Essays  on  the  Intellectual  Powers,"  Essay  II.,  chap.  16.  Reid 
himself,  especially  in  this  work,  has  not  been  always  rigid  in  observ- 
ing their  discrimination. — H. 

j-  Not  only  are  they  different,  but — what  has  escaped  our  philos- 
ophers  the  law  of  their  manifestation  is,  that,  while  both  are  co-ex- 
istent, each  is  always  in  the  inverse  ratio  of  the  other.  Perception 
is  the  objective,  Sensation  the  subjective,  element.  This  by  the 
way.-H. 


288  THE  PHILOSOPHY  OF  REID.  [Cn.  VI. 

The  purposes  of  common  life  do  not  make  it  necessary  to 
distinguish  them,  and  the  received  opinions  of  philos- 
ophers tend  rather  to  confound  them;  but,  without  at- 
tending carefully  to  this  distinction,  it  is  impossible  to 
have  any  just  conception  of  the  operations  of  our  senses. 
The  most  simple  operations  of  the  mind,  admit  not  of  a 
logical  definition:  all  we  can  do  is  to  describe  them,  so  as 
to  lead  those  who  are  conscious  of  them  in  themselves,  to 
attend  to  them,  and  reflect  upon  them;  and  it  is  often 
very  difficult  to  describe  them  so  as  to  answer  this 
intention. 

The  same  mode  of  expression  is  used  to  denote  sensation 
and  perception;  and,  therefore,  we  are  apt  to  look  upon 
them  as  things  of  the  same  nature.  Thus,  I  feel  a  pain; 
I  see  a  tree:  the  first  denoteth  a  sensation,  the  last  a  per- 
ception. The  grammatical  analysis  of  both  expressions 
is  the  same:  for  both  consist  of  an  active  verb  and  an  ob- 
ject. But  if  we  attend  to  the  things  signified  by  these 
expressions,  we  shall  find  that,  in  the  first,  the  distinction 
between  the  act  and  the  object  is  not  real  but  grammatical ; 
in  the  second,  the  distinction  is  not  only  grammatical 
but  real. 

The  form  of  the  expression,  I  feel  pain,  might  seem 
to  imply  that  the  feeling  is  something  distinct  from  the 
pain  felt;  yet,  in  reality,  there  is  no  distinction.  As 
thinking  a  thought  is  an  expression  which  could  signify- 
no  more  than  thinking,  so  feeling  a  pain  signifies  no  more 
than  being  pained.  What  we  have  said  of  pain  is  applica- 
ble to  every  other  mere  sensation.  It  is  difficult  to  give 
instances,  very  few  of  our  sensations  having  names;  and, 
where  they  have,  the  name  being  common  to  the  sensa- 
tion, and  to  something  else  which  is  associated  with  it. 
But,  when  we  attend  to  the  sensation  by  itself,  and  sep- 
arate it  from  other  things  which  are  conjoined  with  it  in 
the  imagination,  it  appears  to  be  something  which  can 
have  no  existence  but  in  a  sentient  mind,  no  distinction 
from  the  act  of  the  mind  by  which  it  is  felt. 


SEC.  XX.]  THE  PHILOSOPHY  OF   REID.  289 

Perception,  as  we  here  understand  it,  hath  always  an 
object  distinct  from  the  act  by  which  it  is  perceived;  an 
object  which  may  exist  whether  it  be  perceived  or  not. 
I  perceive  a  tree  that  grows  before  my  window;  there  is 
here  an  object  which  is  perceived,  and  an  act  of  the 
mind  by  which  it  is  perceived;  and  these  two  are  not 
only  distinguishable,  but  they  are  extremely  unlike  in 
their  natures.  The  object  is  made  up  of  a  trunk, 
branches,  and  leaves;  but  the  act  of  the  mind  by  which 
it  is  perceived  hath  neither  trunk,  branches,  nor  leaves. 
I  am  conscious  of  this  act  of  my  mind,  and  I  can  reflect 
upon  it;  but  it  is  too  simple  to  admit  of  an  analysis, 
and  I  cannot  find  proper  words  to  describe  it.  I  find 
nothing  that  resembles  it  so  much  as  the  remembrance  of 
the  tree,  or  the  imagination  of  it.  Yet  both  these  differ 
essentially  from  perception;  they  differ  likewise  one 
from  another.  It  is  in  vain  that  a  philosopher  assures 
me,  that  the  imagination  of  the  tree,  the  remembrance  of 
it,  and  the  perception  of  it,  are  all  one,  and  differ  only 
in  degree  of  vivacity.  I  know  the  contrary;  for  I  am  as 
well  acquainted  with  all  the  three  as  I  am  with  the  apart- 
ments of  my  own  house.  I  know  this  also,  that  the 
perception  of  an  object  implies  both  a  conception  of  its 
form,  and  a  belief  of  its  present  existence.*  I  know, 
moreover,  that  this  belief  is  not  the  effect  of  argumenta- 


*  It  is  to  be  observed  that  Reid  himself  does  not  discriminate  percep- 
tion and  imagination  by  any  essential  difference.  According  to  him, 
perception  is  only  the  conception  (imagination)  of  an  object,  ac- 
companied with  a  belief  of  its  present  existence;  and  even  this  last 
distinction,  a  mere  "faith  without  knowledge,"  is  surrendered  by 
Mr.  Stewart.  Now,  as  conception  (imagination)  is  only  immedi- 
ately cognisant  of  the  ego,  so  must  perception  on  this  doctrine  be  a 
knowledge  purely  subjective.  Perception  must  be  wholly  different 
in  kind  from  Conception,  if  we  are  to  possess  a  faculty  informing  us 
of  the  existence  and  qualities  of  an  external  world;  and,  unless  we 
are  possessed  of  such  a  faculty,  we  shall  never  be  competent  to  vin- 
dicate more  than  an  ideal  reality  to  the  objects  of  our  cognitions. — H. 


290  THE  PHILOSOPHY   OF  REID.  [Cn.  VI. 

tion  and  reasoning;  it  is  the  immediate  effect  of  my 
constitution. 

I  am  aware  that  this  belief  which  I  have  in  perception 
stands  exposed  to  the  strongest  batteries  of  scepticism. 
But  they  make  no  great  impression  upon  it.  The  scep- 
tic asks  me,  Why  do  you  believe  the  existence  of  the 
external  object  which  you  perceive?  This  belief,  sir, 
is  none  of  my  manufacture;  it  came  from  the  mint  of 
Nature;  it  bears  her  image  and  superscription;  and,  if 
it  is  not  right,  the  fault  is  not  mine:  I  even  took  it  upon 
trust,  and  without  suspicion.  Reason,  says  the  sceptic, 
is  the  only  judge  of  truth,  and  you  ought  to  throw  off 
every  opinion  and  every  belief  that  is  not  grounded  on 
reason.  Why,  sir,  should  I  believe  the  faculty  of  rea- 
son more  than  that  of  perception  ? — they  came  both  out 
of  the  same  shop,  and  were  made  by  the  same  artist; 
and  if  he  puts  one  piece  of  false  ware  into  my  hands, 
what  should  hinder  him  from  putting  another?* 

Perhaps  the  sceptic  will  agree  to  distrust  reason, 
rather  than  give  any  credit  to  perception.  For,  says 
he,  since,  by  your  own  concession,  the  object  which  you 
perceive,  and  that  act  of  your  mind  by  which  you  per- 
ceive it,  are  quite  different  things,  the  one  may  exist 
without  the  other;  and,  as  the  object  may  exist  without 
being  perceived,  so  the  perception  may  exist  without  an 
object.  There  is  nothing  so  shameful  in  a  philosopher 
as  to  be  deceived  and  deluded;  and,  therefore,  you 
ought  to  resolve  firmly  to  withhold  assent,  and  to  throw 
off  this  belief  of  external  objects,  which  may  be  all  delu- 
sion. For  my  part,  I  will  never  attempt  to  throw  it  off; 
and,  although  the  sober  part  of  mankind  will  not  be 

*  This  argument  would  be  good  in  favour  of  our  belief,  that  we 
are  really  percipient  of  a  non-ego:  it  is  not  good  in  favour  of  our 
belief  that  a  non-ego  really  exists,  our  perception  of  its  real  existence 
oeing  abandoned.  Mankind  have  the  latter  belief  only  as  they  have 
the  former;  and,  if  we  are  deceived  by  our  Nature  touching  the  one, 
it  is  absurd  to  appeal  to  her  veracity  in  proof  of  the  other. — H. 


SEC.  XX.]  THE  PHILOSOPHY  OF  REID.  291 

very  anxious  to  know  my  reasons,  yet,  if  they  can  be  of 
use  to  any  sceptic,  they  are  these:— 

First,  because  it  is  not  in  my  power:  why,  then,  should 
I  make  a  vain  attempt  ?  It  would  be  agreeable  to  fly 
to  the  moon,  and  to  make  a  visit  to  Jupiter  and  Saturn; 
but,  when  I  know  that  Nature  has  bound  me  down  by 
the  law  of  gravitation  to  this  planet  which  I  inhabit,  I 
rest  contented,  and  quietly  suffer  myself  to  be  carried 
along  in  its  orbit.  My  belief  is  carried  along  by  per- 
ception, as  irresistibly  as  my  body  by  the  earth.  And 
the  greatest  sceptic  will  find  himself  to  be  in  the  same 
condition.  He  may  struggle  hard  to  disbelieve  the  in- 
formations of  his  senses,  as  a  man  does  to  swim  against 
a  torrent;  but,  ah  !  it  is  in  vain.  It  is  in  vain  that  he 
strains  every  nerve,  and  wrestles  with  nature,  and  with 
every  object  that  strikes  upon  his  senses.  For,  after  all, 
when  his  strength  is  spent  in  the  fruitless  attempt,  he 
will  be  carried  down  the  torrent  with  the  common  herd 
of  believers. 

Secondly,  I  think  it  would  not  be  prudent  to  throw 
off  this  belief,  if  it  were  in  my  power.  If  Nature  in- 
tended to  deceive  me,  and  impose  upon  me  by  false  ap- 
pearances, and  I,  by  my  great  cunning  and  profound 
logic,  have  discovered  the  imposture,  prudence  would 
dictate  to  me,  in  this  case,  even  to  put  up  [with]  this 
indignity  done  me,  as  quietly  as  I  could,  and  not  to  call 
her  an  impostor  to  her  face,  lest  she  should  be  even 
with  me  in  another  way.  For  what  do  I  gain  by  resent- 
ing this  injury  ?  You  ought  at  least  not  to  believe  what 
she  says.  This  indeed  seems  reasonable,  if  she  intends 
to  impose  upon  me.  But  what  is  the  consequence  ? 
I  resolve  not  to  believe  my  senses.  I  break  my  nose 
against  a  post  that  comes  in  my  way;  I  step  into  a  dirty 
kennel;  and,  after  twenty  such  wise  and  rational  actions, 
I  am  taken  up  and  clapped  into  a  mad-house.  Now,  I 
confess  I  would  rather  make  one  of  the  credulous  fools 
whom  Nature  imposes  upon,  than  of  those  wise  and  ra- 


292  THE   PHILOSOPHY   OF   REID.  [Cn.  VI. 

tional  philosophers  who  resolve  to  withhold  assent  at  all 
this  expense.  If  a  man  pretends  to  be  a  sceptic  with 
regard  to  the  informations  of  sense,  and  yet  prudently 
keeps  out  of  harm's  way  as  other  men  do,  he  must 
excuse  my  suspicion,  that  he  either  acts  the  hypocrite,  or 
imposes  upon  himself.  For,  if  the  scale  of  his  belief 
were  so  evenly  poised  as  to  lean  no  more  to  one  side 
than  to  the  contrary,  it  is  impossible  that  his  actions 
could  be  directed  by  any  rules  of  common  prudence.* 

Thirdly,  Although  the  two  reasons  already  mentioned 
are  perhaps  two  more  than  enough,  I  shall  offer  a  third. 
I  gave  implicit  belief  to  the  informations  of  Nature  by 
my  senses,  for  a  considerable  part  of  my  life,  before  I 
had  learned  so  much  logic  as  to  be  able  to  start  a  doubt 
concerning  them.  And  now,  when  I  reflect  upon  what 
is  past,  I  do  not  find  that  I  have  been  imposed  upon  by 
this  belief.  I  find  that  without  it  I  must  have  perished  by 
a  thousand  accidents.  I  find  that  without  it  I  should 
have  been  no  wiser  now  than  when  I  was  born.  I  should 
not  even  have  been  able  to  acquire  that  logic  which  sug- 
gests these  sceptical  doubts  with  regard  to  my  senses. 
Therefore,  I  consider  this  instinctive  belief  as  one  of 
the  best  gifts  of  Nature.  I  thank  the  Author  of  my 
being,  who  bestowed  it  upon  me  before  the  eyes  of  my 
reason  were  opened,  and  still  bestows  it  upon  me,  to  be 
my  guide  where  reason  leaves  me  in  the  dark.  And 
now  I  yield  to  the  direction  of  my  senses,  not  from  in- 
stinct only,  but  from  confidence  and  trust  in  a  faithful 
and  beneficent  Monitor,  grounded  upon  the  experience 
of  his  paternal  care  and  goodness. 

In  all  this,  I  deal  with  the  Author  of  my  being,  no 
otherwise  than  I  thought  it  reasonable  to  deal  with  my 
parents  and  tutors.  I  believed  by  instinct  whatever  they 
told  me,  long  before  I  had  the  idea  of  a  lie,  or  thought 


*  This  is  not  a  fair  consequence  of  Idealism;  therefore,  it  is  not  a 
reductio  ad  absurdum, — H. 


SEC.  XX.]  THE  PHILOSOPHY  OF  REID.  293 

of  the  possibility  of  their  deceiving  me.  Afterwards, 
upon  reflection,  I  found  they  had  acted  like  fair  and  hon- 
est people,  who  wished  me  well.  I  found  that,  if  I  had 
not  believed  what  they  told  me,  before  I  could  give  a 
reason  of  my  belief,  I  had  to  this  day  been  little  better 
than  a  changeling.  And  although  this  natural  credulity 
hath  sometimes  occasioned  my  being  imposed  upon  ty 
deceivers,  yet  it  hath  been  of  infinite  advantage  to  me 
upon  the  whole;  therefore,  I  consider  it  as  another 
good  gift  of  Nature.  And  I  continue  to  give  that 
credit,  from  reflection,  to  those  of  whose  integrity  and 
veracity  I  have  had  experience,  which  before  I  gave  from 
instinct. 

There  is  a  much  greater  similitude  than  is  commonly 
imagined,  between  the  testimony  of  nature  given  by  our 
senses,  and  the  testimony  of  men  given  by  language. 
The  credit  we  give  to  both  is  at  first  the  effect  of  instinct 
only.  When  we  grow  up,  and  begin  to  reason  about 
them,  the  credit  given  to  human  testimony  is  restrained 
and  weakened,  by  the  experience  we  have  of  deceit. 
But  the  credit  given  to  the  testimony  of  our  senses,  is 
established  and  confirmed  by  the  uniformity  and  con- 
stancy of  the  laws  of  nature. 

Our  perceptions  are  of  two  kinds:  some  are  natural 
and  original;  others  acquired,  and  the  fruit  of  experi- 
ence. When  I  perceive  that  this  is  the  taste  of  cyder, 
that  of  brandy;  that  this  is  the  smell  of  an  apple,  that  of 
an  orange;  that  this  is  the  noise  of  thunder,  that  the  ring- 
ing of  bells;  this  the  sound  of  a  coach  passing,  that  the 
voice  of  such  a  friend:  these  perceptions,  and  others  of  the 
same  kind,  are  not  original — they  are  acquired.  But 
the  perception  which  I  have,  by  touch,  of  the  hardness 
and  softness  of  bodies,  of  their  extension,  figure,  and 
motion,  is  not  acquired — it  is  original. 

In  all  our  senses,  the  acquired  perceptions  are  many 
more  than  the  original,  especially  in  sight.  By  this  sense 
we  perceive  originally  the  visible  figure  and  colour  of 


294  THE  PHILOSOPHY  OF  REID.  [Cn.  VI. 

bodies  only,  and  their  visible  place:  *  but  we  learn  to 
perceive  by  the  eye,  almost  everything  which  we  can  per- 
ceive by  touch.  The  original  perceptions  of  this  sense 
serve  only  as  signs  to  introduce  the  acquired. 

The  signs  by  which  objects  are  presented  to  us  in  per- 
ception, are  the  language  of  Nature  to  man  ;  and  as,  in 
many  respects,  it  hath  great  affinity  with  the  language  of 
man  to  man,  so  particularly  in  this,  that  both  are  partly 
natural  and  original,  partly  acquired  by  custom.  Our 
original  or  natural  perceptions  are  analogous  to  the  natu- 
ral language  of  man  to  man,  of  which  we  took  notice  in 
the  fourth  chapter  ;  and  our  acquired  perceptions  are  an- 
alogous to  artificial  language,  which,  in  our  mother- 
tongue,  is  got  very  much  in  the  same  manner  with  our 
acquired  perceptions — as  we  shall  afterwards  more  fully 
explain. 

Not  only  men,  but  children,  idiots,  and  brutes,  acquire 
by  habit  many  perceptions  which  they  had  not  originally. 
Almost  every  employment  in  life  hath  perceptions  of 
this  kind  that  are  peculiar  to  it.  The  shepherd  knows 
every  sheep  of  his  flock,  as  we  do  our  acquaintance,  and 
can  pick  them  out  of  another  flock  one  by  one.  The 
butcher  knows  by  sight  the  weight  and  quality  of  his 
beeves  and  sheep  before  they  are  killed.  The  farmer 
perceives  by  his  eye,  very  nearly,  the  quantity  of  hay  in 
a  rick,  or  of  corn  in  a  heap.  The  sailor  sees  the  burthen, 
the  built,  and  the  distance  of  a  ship  at  sea,  while  she  is 
a  great  way  off.  Every  man  accustomed  to  writing,  dis- 
tinguishes his  acquaintance  by  their  handwriting,  as  he 
does  by  their  faces.  And  the  painter  distinguishes,  in 
the  works  of  his  art,  the  style  of  all  the  great  masters.  In 
a  word,  acquired  perception  is  very  different  in  different 
persons,  according  to  the  diversity  of  objects  about  which 
they  are  employed,  and  the  application  they  bestow  'in 
observing  them. 

*  In  this  passage  Reid  admits  Figure  and  Place  (consequently, 
Extension)  to  be  original  perceptions  of  vision, 


SEC.  XX.]  THE  PHILOSOPHY  OF  REID.  2Q5 

Perception  ought  not  only  to  be  distinguished  from 
sensation,  but  likewise  from  that  knowledge  of  the  objects 
of  sense  which  is  got  by  reasoning.  There  is  no  reason- 
ing in  perception,  as  hath  been  observed.  The  belief 
which  is  implied  in  it,  is  the  effect  of  instinct.  But  there 
are  many  things,  with  regard  to  sensible  objects,  which 
we  can  infer  from  what  we  perceive  ;  and  such  conclu- 
sions of  reason  ought  to  be  distinguished  from  what  is 
merely  perceived.  When  I  look  at  the  moon,  I  perceive 
her  to  be  sometimes  circular,  sometimes  horned,  and 
sometimes  gibbous.  This 'is  simple  perception,  and  is 
the  same  in  the  philosopher  and  in  the  clown :  but  from 
these  various  appearances  of  her  enlightened  part,  I  infer 
that  she  is  really  of  a  spherical  figure.  This  conclusion 
is  not  obtained  by  simple  perception,  but  by  reasoning. 
Simple  perception  has  the  same  relation  to  the  conclu- 
sions of  reason  drawn  from  our  perceptions,  as  the  axioms 
in  mathematics  have  to  the  propositions.  I  cannot  de- 
monstrate that  two  quantities  which  are  equal  to  the  same 
quantity,  are  equal  to  each  other ;  neither  can  I  demon- 
strate that  the  tree  which  I  perceive,  exists.  But,  by  the 
constitution  of  my  nature,  my  belief  is  irresistibly  car- 
ried along  by  my  apprehension  of  the  axiom  ;  and,  by 
the  constitution  of  my  nature,  my  belief  is  no  less  irre- 
sistibly carried  along  by  my  perception  of  the  tree.  All 
reasoning  is  from  principles.  The  first  principles  of  ma- 
thematical reasoning  are  mathematical  axioms  -and  def- 
initions ;  and  the  first  principles  of  all  our  reasoning 
about  existences,  are  our  perceptions.  The  first  princi- 
ples of  every  kind  of  reasoning  are  given  us  by  Nature, 
and  are  of  equal  authority  with  the  faculty  of  reason  it- 
self, which  is  also  the  gift  of  Nature.  The  conclusions 
of  reason  are  all  built  upon  first  principles,  and  can  have 
no  other  foundation.  Most  justly,  therefore,  do  such 
principles  disdain  to  be  tried  by  reason,  and  laugh  at  all 
the  artillery  of  the  logician,  when  it  is  directed  against 
them. 


296  THE  PHILOSOPHY   OF  REID.  [Cn.  VI. 

When  a  long  train  of  reasoning  is  necessary  in  demon- 
strating a  mathematical  proposition,  it  is  easily  distin- 
guished from  an  axiom ;  and  they  seem  to  be  things  of 
a  very  different  nature.  But  there  are  some  propositions 
which  lie  so  near  to  axioms,  that  it  is  difficult  to  say 
whether  they  ought  to  be  held  as  axioms,  or  demonstrated 
as  propositions.  The  same  thing  holds  with  regard  to 
perception,  and  the  conclusions  drawn  from  it.  Some 
of  these  conclusions  follow  our  perceptions  so  easily,  and 
are  so  immediately  connected  with  them,  that  it  is  diffi- 
cult to  fix  the  limit  which  divides  the  one  from  the 
other. 

Perception,  whether  original  or  acquired,  implies  no 
exercise  of  reason ;  and  is  common  to  men,   children, 
idiots,  and  brutes.     The  more  obvious  conclusions  drawn 
from  our  perceptions,  by  reason,  make  what  we  call  com- 
mon understanding;  by  which  men  conduct  themselves  in 
the  common  affairs  of  life,  and  by  which  they  are  dis- 
tinguished from  idiots.      The  more  remote  conclusions 
which  are  drawn  from  our  perceptions,  by  reason,  make 
what  we  commonly  call  science  in  the  various  parts  of  na- 
ture, whether  in  agriculture,  medicine,  mechanics,  or  in 
any  part  of  natural  philosophy.     When  I  see  a  garden 
in  good  order,  containing  a  great  variety  of  things  of  the 
best  kinds,  and  in  the  most  flourishing  condition,  I  im- 
mediately conclude  from  these  signs  the  skill  and  indus- 
try  of  the   gardener.     A   farmer,  when   he  rises  in  the 
morning,   and   perceives  that  the   neighbouring   brook 
overflows  his  field,  concludes  that   a  great  deal  of  rain 
hath  fallen  in  the  night.     Perceiving  his  fence  broken, 
and  his  corn  trodden  down,  he  concludes  that  some  of 
his  own  or  his  neighbours'  cattle  have  broke  loose.     Per- 
ceiving that  his  stable-door  is  broke  open,  and  some  of 
his  horses  gone,  he  concludes  that  a  thief  has   carried 
them  off.     He  traces  the  prints  of  his  horses'  feet  in  the 
soft  ground,  and  by  them  discovers  which  road  the  thief 
hath  taken.     These  are  instances  of  common  understand- 


SEC.  XXI.]  THE  PHILOSOPHY  OF  REID.  297 

ing,  which  dwells  so  near  to  perception  that  it  is  difficult 
to  trace  the  line  which  divides  the  one  from  the  other. 
In  like  manner  the  science  of  nature  dwells  so  near  to 
common  understanding  that  we  cannot  discern  where  the 
latter  ends  and  the  former  begins.  I  perceive  that  bodies 
lighter  than  water  swim  in  water,  and  that  those  which 
are  heavier  sink.  Hence  I  conclude,  that,  if  a  body  re- 
mains wherever  it  is  put  under  water,  whether  at  the  top 
or  bottom,  it  is  precisely  of  the  same  weight  with  water. 
If  it  will  rest  only  when  part  of  it  is  above  water,  it  is 
lighter  than  water.  And  the  greater  the  part  above  water 
is,  compared  with  the  whole,  the  lighter  is  the  body.  If 
it  had  no  gravity  at  all,  it  would  make  no  impression 
upon  the  water,  but  stand  wholly  above  it.  Thus,  every 
man,  by  common  understanding,  has  a  rule  by  which  he 
judges  of  the  specific  gravity  of  bodies  which  swim  in 
water  ;  and  a  step  or  two  more  leads  him  into  the  science 
of  hydrostatics. 

All  that  we  know  of  nature,  or  of  existences,  may  be 
compared  to  a  tree,  which  hath  its  root,  trunk,  and 
branches.  In  this  tree  of  knowledge,  perception  is  the 
root,  common  understanding  is  the  trunk,  and  the  sci- 
ences are  the  branches. 

Section   XXL 

OF   THE    PROCESS    OF    NATURE    IN    PERCEPTION. 

Although  there  is  no  reasoning  in  perception,  yet  there 
are  certain  means  and  instruments,  which,  by  the  ap- 
pointment of  nature,  must  intervene  between  the  object 
and  our  perception  of  it :  and,  by  these,  our  perceptions 
are  limited  and  regulated.  First,  if  the  object  is  not  in  con- 
tact with  the  organ  of  sense,  there  must  be  some  medium 
which  passes  between  them.  Thus,  in  vision,  the  rays 
of  light ;  in  hearing,  the  vibrations  of  elastic  air ;  in 
smelling,  the  effluvia  of  the  body  smelled — must  pass 


298  THE  PHILOSOPHY  OF  REID.  |Cn.  VI. 

from  the  object  to  the  organ  ;  otherwise  we  have  no  per- 
ception. *  Secondly,  There  must  be  some  action  or  im- 
pression upon  the  organ  of  sense,  either  by  the  immedi- 
ate application  of  the  object,  or  by  the  medium  that  goes 
between  them.  Thirdly,  The  nerves  which  go  from  the 
brain  to  the  organ  must  receive  some  impression  by 
means  of  that  which  was  made  upon  the  organ  ;  and, 
probably,  by  means  of  the  nerves,  some  impression  must 
be  made  upon  the  brain.  Fourthly,  The  impression 
made  upon  the  organ,  nerves,  and  brain,  is  followed  by 
a  sensation.  And,  last  of  all,  This  sensation  is  followed 
by  the  perception  of  the  object. 

Thus,  our  perception  of  objects  is  the  result  of  a  train 
of  operations  ;  some  of  which  affect  the  body  only,  others 
affect  the  mind.  We  know  very  little  of  the  nature  of 
some  of  these  operations  ;  we  know  not  at  all  how  they 
are  connected  together,  or  in  what  way  they  contribute 
to  that  perception  which  is  the  result  of  the  whole  ;  but, 
by  the  laws  of  our  constitution,  we  perceive  objects  in 
this  and  in  no  other  way. 

There  may  be  other  beings  who  can  perceive  external 
objects  without  rays  of  light,  or  vibrations  of  air,  or  efflu- 
via of  bodies — without  impressions  on  bodily  organs,  or 
even  without  sensations;  but  we  are  so  framed  by  the 
Author  of  Nature,  that  even  when  we  are  surrounded  by  ex- 
ternal objects,  we  may  perceive  none  of  them  Our  faculty 
of  perceiving  an  object  lies  dormant,  until  it  is  roused  and 
stimulated  by  a  certain  corresponding  sensation.  Nor  is 
this  sensation  always  at  hand  to  perform  its  office ;  for  it 
enters  into  the  mind  only  in  consequence  of  a  certain 
corresponding  impression  made  on  the  organ  of  sense  by 
the  object. 


*  The  only  object  of  perception  is  the  immediate  object.  The 
distant  reality— the  mediate  object,  or  object  simply  of  Reid  and 
other  philosophers — is  unknown  to  the  perception  of  sense,  and  only 
reached  by  reasoning. — H. 


SEC.  XXI.]  THE  PHILOSOPHY  OF  REID.  299 

Let  us  trace  this  correspondence  of  impressions,  sen- 
sations, and  perceptions,  as  far  as  we  can — beginning  with 
that  which  is  first  in  order,  the  impression  made  upon 
the  bodily  organ.  But,  alas  !  we  know  not  of  what  na- 
ture these  impressions  are,  far  less  how  they  excite  sensa- 
tions in  the  mind. 

We  know  that  one  body  may  act  upon  another  by 
pressure,  by  percussion,  by  attraction,  by  repulsion,  and, 
probably,  in  many  other  ways  which  we  neither  know  nor 
have  names  to  express.  But  in  which  of  these  ways  ob- 
jects, when  perceived  by  us,  act  upon  the  organs  of  sense, 
these  organs  upon  the  nerves,  and  the  nerves  upon  the 
brain,  we  know  not.  Can  any  man  tell  me  how  in  vis- 
ion, the  rays  of  light  act  upon  the  retina,  how  the  retina 
acts  upon  the  optic  nerve,  and  how  the  optic  nerve  acts 
upon  the  brain  ?  No  man  can.  When  I  feel  the  pain 
of  the  gout  in  my  toe,  I  know  that  there  is  some  un- 
usual impression  made  upon  that  part  of  my  body.  But 
of  what  kind  is  it?  Are  the  small  vessels  distended  with 
some  redundant  elastic,  or  unelastic  fluid  ?  Are  the  fi- 
bres unusually  stretched?  Are  they  torn  asunder  by  force, 
or  gnawed  and  corroded  by  some  acrid  humour  ?  I  can 
answer  none  of  these  questions.  All  that  I  feel  is  pain, 
which  is  not  an  impression  upon  the  body,  but  upon  the 
mind ;  and  all  that  I  perceive  by  this  sensation  is,  that 
some  distemper  in  my  toe  occasions  this  pain.  But  as  I 
know  not  the  natural  temper  and  texture  of  my  toe  when 
it  is  at  ease,  I  know  as  little  what  change  or  disorder  of 
its  parts  occasions  this  uneasy  sensation.  In  like  manner, 
in  every  other  sensation,  there  is,  without  doubt,  some 
impression  made  upon  the  organ  of  sense ;  but  an  im- 
pression of  which  we  know  not  the  nature.  It  is  too 
subtile  to  be  discovered  by  our  senses,  and  we  may  make 
a  thousand  conjectures  without  coming  near  the  truth. 
If  we  understood  the  structure  of  our  organs  of  sense  so 
minutely  as  to  discover  what  effects  are  produced  upon 
them  by  external  objects,  this  knowledge  would  contrib- 


300  THE  PHILOSOPHY  OF  REID.  [Cn.  VI. 

ute  nothing  to  our  perception  of  the  object ;  for  they 
perceive  as  distinctly  who  know  least  about  the  manner 
of  perception,  as  the  greatest  adepts.  It  is  necessary  that 
the  impression  be  made  upon  our  organs,  but  not  that 
it  be  known.  Nature  carries  on  this  part  of  the  process 
of  perception,  without  our  consciousness  or  concurrence. 

But  we  cannot  be  unconscious  of  the  next  step  in  this 
process — the  sensation  of  the  mind,  which  always  im- 
mediately follows  the  impression  made  upon  the  body. 
It  is  essential  to  a  sensation  to  be  felt,  and  it  can  be 
nothing  more  than  we  feel  it  to  be.  If  we  can  only 
acquire  the  habit  of  attending  to  our  sensations,  we  may 
know  them  perfectly.  But  how  are  the  sensations  of 
the  mind  produced  by  impressions  upon  the  body  ?  Of 
this  we  are  absolutely  ignorant,  having  no  means  of 
knowing  how  the  body  acts  upon  the  mind,  or  the  mind 
upon  the  body.  When  we  consider  the  nature  and  at- 
tributes of  both,  they  seem  to  be  so  different,  and  so 
unlike,  that  we  can  find  no  handle  by  which  the  one  may 
lay  hold  of  the  other.  There  is  a  deep  and  a  dark  gulf 
between  them,  which  our  understanding  cannot  pass; 
and  the  manner  of  their  correspondence  and  intercourse 
is  absolutely  unknown. 

Experience  teaches  us,  that  certain  impressions  upon 
the  body  are  constantly  followed  by  certain  sensations  of 
the  mind;  and  that,  on  the  other  hand,  certain  deter- 
minations of  the  mind  are  constantly  followed  by  cer- 
tain motions  in  the  body;  but  we  see  not  the  chain  that 
ties  these  things  together.  Who  knows  but  their  con- 
nection may  be  arbitrary,  and  owing  to  the  will  of  our 
Maker  ?  Perhaps  the  same  sensations  might  have  been 
connected  with  other  impressions,  or  other  bodily  organs. 
Perhaps  we  might  have  been  so  made  as  to  taste  with 
our  fingers,  to  smell  with  our  ears,  and  to  hear  by  the 
nose.  Perhaps  we  might  have  been  so  made  as  to  have 
all  the  sensations  and  perceptions  which  we  have,  with- 
out any  impression  made  upon  our  bodily  organs  at  all. 


Sfic.XXI.l  THE  PHILOSOPHY  OF  REID.  301 

However  these  things  may  be,  if  Nature  had  given  us 
nothing  more  than  impressions  made  upon  the  body,  and 
sensations  in  our  minds  corresponding  to  them,  \ve 
should,  in  that  case,  have  been  merely  sentient,  but  not 
percipient  beings.  We  should  never  have  been  able  to 
form  a  conception  of  any  external  object,  far  less  a  be- 
lief of  its  existence.  Our  sensations  have  no  resemblance 
to  external  objects;  nor  can  we  discover,  by  our  reason, 
any  necessary  connection  between  the  existence  of  the 
former,  and  that  of  the  latter. 

We  might,  perhaps,  have  been  made  of  such  a  con- 
stitution as  to  have  our  present  perceptions  connected 
with  other  sensations.  We  might,  perhaps,  have  had 
the  perception  of  external  objects,  without  either  impres- 
sions upon  the  organs  of  sense,  or  sensations.  Or,  lastly, 
The  perceptions  we  have,  might  have  been  immediately 
connected  with  the  impressions  upon  our  organs,  with- 
out any  intervention  of  sensations.  This  last  seems 
really  to  be  the  case  in  one  instance — to  wit,  in  our  per- 
ception of  the  visible  figure  of  bodies,  as  was  observed  in 
the  eighth  section  of  this  chapter. 

The  process  of  Nature,  in  perception  by  the  senses, 
may,  therefore,  be  conceived  as  a  kind  of  drama,  wherein 
some  things  are  performed  behind  the  scenes,  others  are 
represented  to  the  mind  in  different  scenes,  one  succeed- 
ing another.  The  impression  made  by  the  object  upon 
the  organ,  either  by  immediate  contact  or  by  some  in- 
tervening medium,  as  well  as  the  impression  made  upon 
the  nerves  and  brain,  is  performed  behind  the  scenes, 
and  the  mind  sees  nothing  of  it.  But  every  such  im- 
pression, by  the  laws  of  the  drama,  is  followed  by  a  sen- 
sation, which  is  the  first  scene  exhibited  to  the  mind; 
and  this  scene  is  quickly  succeeded  by  another,  which 
is  the  perception  of  the  object. 

In  this  drama,  Nature  is  the  actor,  we  are  the  specta- 
tors. We  know  nothing  of  the  machinery  by  means  of 
which  every  different  impression  upon  the  organ,  nerves, 


302  THE  PHILOSOPHY  OF  REID.  [CH.VI. 

and  brain,  exhibits  its  corresponding  sensation;  or  of  the 
machinery  by  means  of  which  each  sensation  exhibits  its 
corresponding  perception.  We  are  inspired  with  the 
sensation,  and  we  are  inspired  with  the  corresponding 
perception,  by  means  unknown.*  And,  because  the 
mind  passes  immediately  from  the  sensation  to  that  con- 
ception and  belief  of  the  object  which  we  have  in  percep- 
tion, in  the  same  manner  as  it  passes  from  signs  to  the 
things  signified  by  them,  we  have,  therefore,  called  our 
sensations  signs  of  external  objects;  finding  no  word  more 
proper  to  express  the  function  which  Nature  hath 
assigned  them  in  perception,  and  the  relation  which  they 
bear  to  their  corresponding  objects. 

There  is  no  necessity  of  a  resemblance  between  the 
sign  and  the  thing  signified  ;  and  indeed  no  sensation 
can  resemble  any  external  object.  But  there  are  two 
things  necessary  to  our  knowing  things  by  means  of  signs. 
First,  That  a  real  connection  between  the  sign  and  thing 
signified  be  established,  either  by  the  course  of  nature, 
or  by  the  will  and  appointment  of  men.  When  they  are 
•connected  by  the  course  of  nature,  it  is  a  natural  sign; 
when  by  human  appointment,  it  is  an  artificial  sign. 
Thus,  smoke  is  a  natural  sign  of  fire;  certain  features  are 
natural  signs  of  anger:  but  our  words,  whether  ex- 
pressed by  articulate  sounds  or  by  writing,  are  artificial 
signs  of  our  thoughts  and  purposes. 

Another  requisite  to  our  knowing  things  by  signs  is, 
that  the  appearance  of  the  sign  to  the  mind,  be  followed 
by  the  conception  and  belief  of  the  thing  signified. 
Without  this,  the  sign  is  not  understood  or  interpreted; 
and,  therefore,  is  no  sign  to  us,  however  fit  in  its  own 
nature  for  that  purpose. 

Now,  there  are  three  ways  in  which  the  mind  passes 
from  the  appearance  of  a  natural  sign  to  the  conception 

*  On  perception  as  a  revelation — "a  miraculous  revelation  "—see 
Jacobi's  "  David  Hume."— H. 


SEC.  XXII.]  THE  PHILOSOPHY  OF  REID.  303 

and  belief  of  the  thing  signified — by  original  principles  of 
our  constitution,  by  custom  and  by  reasoning. 

Our  original  perceptions  are  got  in  the  first  of  these 
ways,  our  acquired  perceptions  in  the  second,  and  all 
that  reason  discovers  of  the  course  of  nature,  in  the  third. 
In  the  first  of  these  ways,  Nature,  by  means  of  the  sensa- 
tions of  touch,  informs  us  of  the  hardness  and  softness 
of  bodies;  of  their  extension,  figure,  and  motion;  and  of 
that  space  in  which  they  move  and  are  placed — as  hath 
been  already  explained  in  the  fifth  chapter  of  this  inquiry. 
And,  in  the  second  of  these  ways,  she  informs  us,  by 
means  of  our  eyes,  of  almost  all  the  same  things  which 
originally  we  could  perceive  only  by  touch. 

In  order,  therefore,  to  understand  more  particularly 
how  we  learn  to  perceive  so  many  things  by  the  eye, 
which  originally  could  be  perceived  only  by  touch,  it  will 
be  proper,  First,  To  point  out  the  signs  by  which  those 
things  are  exhibited  to  the  eye,  and  their  connection  with 
the  things  signified  by  them;  and,  Secondly,  To  consider 
how  the  experience  of  this  connection  produces  that 
habit  by  which  the  mind,  without  any  reasoning  or  re- 
flection, passes  from  the  sign  to  the  conception  and  be- 
lief of  the  thing  signified. 

Of  all  the  acquired  perceptions  which  we  have  by  sight, 
the  most  remarkable  is  the  perception  of  the  distance  of 
objects  from  the  eye;  we  shall,  therefore,  particularly 
consider  the  signs  by  which  this  perception  is  exhibited, 
and  only  make  some  general  remarks  with  regard  to  the 
signs  which  are  used  in  other  acquired  perceptions. 

Section  XXII. 

OF  THE  SIGNS  BY  WHICH    WE    LEARN    TO    PERCEIVE    DISTANCE 
FROM  THE  EYE. 

It  was  before  observed  in  general,  that  the  original 
perceptions  of  sight  are  signs  which  serve  to  introduce 


304  THE  PHILOSOPHY  OF  REID.  [Cn.  VI. 

those  thaf  are  acquired;  but  this  is  not  to  be  understood 
as  if  no  other  signs  were  employed  for  that  purpose. 
There  are  several  motions  of  the  eyes,  which,  in  order  to 
distinct  vision,  must  be  varied,  according  as  the  object 
is  more  or  less  distant;  and  such  motions  being  by  habit 
connected  with  the  corresponding  distances  of  the  object, 
become  signs  of  those  distances.  These  motions  were  at 
first  voluntary  and  unconfmed;  but,  as  the  intention  of 
nature  was  to  produce  perfect  and  distinct  vision  by  their 
means,  we  soon  learn  by  experience  to  regulate  them 
according  to  that  intention  only,  without  the  least  reflec- 
tion. 

A  ship  requires  a  different  trim  for  every  variation  of 
the  direction  and  strength  of  the  wind;  and,  if  we  may 
be  allowed  to  borrow  that  word,  the  eyes  require  a  differ- 
ent trim  for  every  degree  of  light,  and  for  every  variation 
of  the  distance  of  the  object,  while  it  is  within  certain 
limits.  The  eyes  are  trimmed  for  a  particular  object,  by 
contracting  certain  muscles  and  relaxing  others;  as  the 
ship  is  trimmed  for  a  particular  wind  by  drawing  certain 
ropes  and  slackening  others.  The  sailor  learns  the  trim 
of  his  ship,  as  we  learn  the  trim  of  our  eyes,  by  expe- 
rience. A  ship,  although  the  noblest  machine  that  hu- 
man art  can  boast,  is  far  inferior  to  the  eye  in  this  re- 
spect, that  it  requires  art  and  ingenuity  to  navigate  her; 
and  a  sailor  must  know  what  ropes  he  must  pull,  and 
what  he  must  slacken,  to  fit  her  to  a  particular  wind; 
but  with  such  superior  wisdom  is  the  fabric  of  the  eye, 
and  the  principles  of  its  motion  contrived,  that  it  requires 
no  art  nor  ingenuity  to  see  by  it.  Even  that  part  of 
vision  which  is  got  by  experience,  is  attained  by  idiots. 
We  need  not  know  what  muscles  we  are  to  contract,  and 
what  we  are  to  relax,  in  order  to  fit  the  eye  to  a  particu- 
lar distance  of  the  object. 

But,  although  we  are  not  conscious  of  the  motions  we 
perform,  in  order  to  fit  the  eyes  to  the  distance  of  the 
object,  we  are  conscious  of  the  effort  employed  in  pro- 


SEC.  XXII.]  THE  PHILOSOPHY  OF  REID.  305 

ducing  these  motions;  and  probably  have  some  sensation 
which  accompanies  them,  to  which  we  give  as  little  at- 
tention as  to  other  sensations.  And  thus,  an  effort  con- 
sciously exerted,  or  a  sensation  consequent  upon  that 
effort,  comes  to  be  conjoined  with  the  distance  of  the 
object  which  gave  occasion  to  it,  and  by  this*  conjunc- 
tion becomes  a  sign  of  that  distance.  Some  instances 
of  this  will  appear  in  considering  the  means  or  signs  by 
which  we  learn  to  see  the  distance  of  objects  from  the 
eye.  In  the  enumeration  of  these,  we  agree  with  Dr. 
Porterfield,  notwithstanding  that  distance  from  the  eye, 
in  his  opinion,  is  perceived  originally,  but,  in  our  opin- 
ion, by  experience  only. 

In  general,  when  a  near  object  affects  the  eye  in  one 
manner,  and  the  same  object,  placed  at  a  greater  dis- 
tance, affects  it  in  a  different  manner,  these  various 
affections  of  the  eye  become  signs  of  the  corresponding 
distances.  The  means  of  perceiving  distance  by  the  eye 
will  therefore  be  explained  by  shewing  in  what  various 
ways  objects  affect  the  eye  differently,  according  to  their 
proximity  or  distance. 

i.  It  is  well  known,  that,  to  see  objects  distinctly  at 
various  distances,  the  form  of  the  eye  must  undergo 
some  change :  and  nature  hath  given  us  the  power  of 
adapting  it  to  near  objects,  by  the  contraction  of  certain 
muscles,  and  to  distant  objects  by  the  contraction  of 
other  muscles.  As  to  the  manner  in  which  this  is  done, 
and  the  muscular  parts  employed,  anatomists  do  not  al- 
together agree.  The  ingenious  Dr.  Jurin,  in  his  excel- 
lent essay  on  distinct  and  indistinct  vision,  seems  to 
have  given  the  most  probable  account  of  this  matter;  and 
to  him  I  refer  the  reader. 

But,  whatever  be  the  manner  in  which  this  change  of 
the  form  of  the  eye  is  effected,  it  is  certain  that  young 
people  have  commonly  the  power  of  adapting  their  eyes 
to  all  distances  of  the  object,  from  six  or  seven  inches, 
to  fifteen  or  sixteen  feet ;  so  as  to  have  perfect  and  dis- 


306  THE  PHILOSOPHY  OF  REID.  [Cn.  VI. 

tinct  vision  at  any  distance  within  these  limits.  From 
this  it  follows,  that  the  effort  we  consciously  employ  to 
adapt  the  eye  to  any  particular  distance  of  objects  within 
these  limits,  will  be  connected  and  associated  with  that 
distance,  and  will  become  a  sign  of  it  When  the  object 
is  removed  beyond  the  farthest  limit  of  distinct  vision,  it 
will  be  seen  indistinctly;  but,  more  or  less  so,  according 
as  its  distance  is  greater  or  less ;  so  that  the  degrees  of 
indistinctness  of  the  object  may  become  the  signs  of  dis- 
tances considerably  beyond  the  farthest  limit  of  distinct 
Vision. 

If  we  had  no  other  mean  but  this,  of  perceiving  dis- 
tance of  visible  objects,  the  most  distant  would  not  ap- 
pear to  be  above  twenty  or  thirty  feet  from  the  eye,  and 
the  tops  of  houses  and  trees  would  seem  to  touch  the 
clouds;  for,  in  that  case,  the  signs  of  all  greater  distances 
being  the  same,  (hey  have  the  same  signification,  and 
give  the  same  perception  of  distance. 

But  it  is  of  more  importance  to  observe,  that,  because 
the  nearest  limit  of  distinct  vision  in  the  time  of  youth, 
when  we  learn  to  perceive  distance  by  the  eye,  is  about 
six  or  seven  inches,  no  object  seen  distinctly  ever  appears 
to  be  nearer  than  six  or  seven  inches  from  the  eye.  We 
can,  by  art,  make  a  small  object  appear  distinct,  when 
it  is  in  reality  not  above  half  an  inch  from  the  eye; 
either  by  using  a  single  microscope,  or  by  looking 
through  a  small  pin-hole  in  a  card.  When,  by  either  of 
these  means,  an  object  is  made  to  appear  distinct,  how- 
ever small  its  distance  is  in  reality,  it  seems  to  be  re- 
moved at  least  to  the  distance  of  six  or  seven  inches — 
that  is,  within  the  limits  of  distinct  vision. 

This  observation  is  the  more  important,  because  it 
affords  the  only  reason  we  can  give  why  an  object  is 
magnified  either  by  a  single  microscope,  or  by  being  seen 
through  a  pin-hole;  and  the  only  mean  by  which  we  can 
ascertain  the  degree  in  which  the  object  will  be  magni- 
fied by  either.  Thus,  if  the  object  is  really  half  an  inch 


SEC.  XXII.]  THE  PHILOSOPHY   OF  REID.  307 

distant  from  the  eye,  and  appears  to  be  seven  inches  dis- 
tant, its  diameter  will  seem  to  be  enlarged  in  the  same  pro- 
portion as  its  distance — that  is,  fourteen  times. 

2.  In  order  to  direct  both  eyes  to  an  object,  the  optic 
axes  must  have  a  greater  or  less  inclination,  according  as 
tha  object  is  nearer  or  more  distant.  And,  although  we 
are  not  conscious  of  this  inclination,  yet  we  are  con- 
scious of  the  effort  employed  in  it.  By  this  mean 
we  perceive  small  distances  more  accurately  than  we 
could  do  by  the  conformation  of  the  eye  only.  And, 
therefore,  we  find,  that  those  who  have  lost  the  sight  of 
one  eye  are  apt,  even  within  arms-length,  to  make  mis- 
takes in  the  distance  of  objects,  which  are  easily  avoided 
by  those  who  see  with  both  eyes.  Such  mistakes  are  of- 
ten discovered  in  snuffing  a  candle,  in  threading  a  nee- 
dle, or  in  filling  a  tea-cup. 

When  a  picture  is  seen  with  both  eyes,  and  at  no 
great  distance,  the  representation  appears  not  so  natural 
as  when  it  is  seen  only  with  one.  The  intention  of 
painting  being  to  deceive  the  eye,  and  to  make  things 
appear  at  different  distances  which  in  reality  are  upon 
the  same  piece  of  canvass,  this  deception  is  not  so  easily 
put  upon  both  eyes  as  upon  one;  because  we  perceive 
the  distance  of  visible  objects  more  exactly  and  deter- 
minately  with  two  eyes  than  with  one.  If  the  shading 
and  relief  be  executed  in  the  best  manner,  the  picture 
may  have  almost  the  same  appearance  to  one  eye  as  the 
objects  themselves  would  have;  but  it  cannot  have  the 
same  appearance  to  both.  This  is  not  the  fault  of  the 
artist,  but  an  unavoidable  imperfection  in  the  art.  And 
it  is  owing  to  what  we  just  now  observed,  that  the  per- 
ception we  have  of  the  distance  of  objects  by  one  eye  is 
more  uncertain,  and  more  liable  to  deception,  than  that 
which  we  have  by  both. 

The  great  impediment,  and  I  think  the  only  invinci- 
ble impediment,  to  that  agreeable  deception  of  the  eye 
which  the  painter  aims  at,  is  the  perception  which  WQ 


308  THE  PHILOSOPHY  OF  REID.  [Cn.  VI. 

have  of  the  distance  of  visible  objects  from  the  eye,  part- 
ly by  means  of  the  conformation  of  the  eye,  but  chiefly 
by  means  of  the  inclination  of  the  optic  axes.  If  this 
perception  could  be  removed,  I  see  no  reason  why  a 
picture  might  not  be  made  so  perfect  as  to  deceive  the 
eye  in  reality,  and  to  be  mistaken  for  the  original  object. 
Therefore,  in  order  to  judge  of  the  merit  of  a  picture, 
we  ought,  as  much  as  possible,  to  exclude  these  two 
means  of  perceiving  the  distance  of  the  several  parts  of  it. 

In  order  to  remove  this  perception  of  distance,  the 
connoisseurs  in  painting  use  a  method  which  is  very 
proper.  They  look  at  the  picture  with  one  eye,  through 
a  tube  which  excludes  the  view  of  all  other  objects.  By 
this  method,  the  principal  mean  whereby  we  perceive  the 
distance  of  the  object — to  wit,  the  inclination  of  the  op- 
tic axes — is  entirely  excluded.  I  would  humbly  pro- 
pose, as  an  improvement  of  this  method  of  viewing  pic- 
tures, that  the  aperture  of  the  tube  next  to  the  eye  should 
be  very  small.  If  it  is  as  small  as  a  pin-hole,  so  much 
the  better,  providing  there  be  light  enough  to  see  the 
picture  clearly.  The  reason  of  this  proposal  is,  that, 
when  we  look  at  an  object  through  a  small  aperture,  it 
will  be  seen  distinctly,  whether  the  conformation  of  the 
eye  be  adapted  to  its  distance  or  not ;  and  we  have  no 
mean  left  to  judge  of  the  distance,  but  the  light  and 
colouring,  which  are  in  the  painter's  power.  If,  there- 
fore, the  artist  performs  his  part  properly,  the  picture 
will  by  this  method  affect  the  eye  in  the  same  manner 
that  the  object  represented  would  do;  which  is  the  per- 
fection of  this  art. 

Although  this  second  mean  of  perceiving  the  distance 
of  visible  objects  be  more  determinate  and  exact  than 
the  first,  yet  it  hath  its  limits,  beyond  which  it  can  be 
of  no  use.  For  when  the  optic  axes  directed  to  an  ob- 
ject are  so  nearly  parallel  that,  in  directing  them  to  an 
object  yet  more  distant,  we  are  not  conscious  of  any  new 
effort,  nor  have  any  different  sensation,  there  our  per- 


SEC.  XXII.]  THE  PHILOSOPHY  OF  REID.  309 

ception  of  distance  stops;  and,  as  all  more  distant  ob- 
jects affect  the  eye  in  the  same  manner,  we  perceive  them 
to  be  at  the  same  distance.  This  is  the  reason  why  the 
sun,  moon,  planets,  and  fixed  stars,  when  seen  not  near 
the  horizon,  appear  to  be  all  at  the  same  distance,  as  if 
they  touched  the  concave  surface  of  a  great  sphere.  The 
surface  of  this  celestial  sphere  is  at  that  distance  beyond 
which  all  objects  affect  the  eye  in  the  same  manner. 
Why  this  celestial  vault  appears  more  distant  towards 
the  horizon,  than  towards  the  zenith,  will  afterwards  ap- 
pear. 

3.  The  colours  of  objects,  according  as  they  are  more  $, 
distant,  become  more  faint  and  languid,  and  are  tinged 
more  with  the  azure  of  the  -intervening  atmosphere:  to 
this  we  may  add,  that  "their  minute  parts  become  more 
indistinct,  and  their  outline  less  accurately  defined.  It  is 
by  these  means  chiefly,  that  painters  can  represent  objects 
at  very  different  distances,  upon  the  same  canvass.  And 
the  diminution  of  the  magnitude  of  an  object  would  not 
have  the  effect  of  making  it  appear  to  be  at  a  great  dis- 
tance, without  this  degradation  of  colour,  and  indistinct- 
ness of  the  outline,  and  of  the  minute  parts.  If  a 
painter  should  make  a  human  figure  ten  times  less  than 
other  human  figures  that  are  in  the  same  piece,  having 
the  colours  as  bright,  and  the  outline  and  minute  parts 
as  accurately  defined,  it  would  not  have  the  appearance 
of  a  man  at  a  great  distance,  but  of  a  pigmy  or  Lilipu- 
tian. 

When  an  object  hath  a  known  variety  of  colours,  its 
distance  is  more  clearly  indicated  by  the  gradual  dilution 
of  the  colours  into  one  another,  than  when  it  is  of  one 
uniform  colour.  In  the  steeple  which  stands  before  me 
at  a  small  distance,  the  joinings  of  the  stones  are  clearly 
perceptible;  the  grey  colour  of  the  stone,  and  the  white 
cement  are  distinctly  limited  :  when  I  see  it  at  a  greater 
distance,  the  joinings  of  the  stones  are  less  distinct,  and 
the  colours  of  the  stone  and  of  the  cement  begin  to  di- 


310  THE  PHILOSOPHY  OF  REID.  (Cn.  VI. 

lute  into  one  another:  at  a  distance  still  greater,  the  join- 
ings disappear  altogether,  and  the  variety  of  colour  van- 
ishes. 

In  an  apple-tree  which  stands  at  the  distance  of  about 
twelve  feet,  covered  with  flowers,  I  can  perceive  the 
figure  and  the  color  of  the  leaves  and  petals  ;  pieces  of 
branches,  some  larger,  others  smaller,  peeping  through 
the  intervals  of  the  leaves — some  of  them  enlightened  by 
the  sun's  rays,  others  shaded  ;  and  some  openings  of  the 
sky  are  perceived  through  the  whole.  When  I  gradu- 
ally remove  from  this  tree,  the  appearance,  even  as  to 
colour,  changes  every  minute.  First,  the  smaller  parts, 
then  the  larger,  are  gradually  confounded  and  mixed. 
The  colours  of  leaves,  petals,  branches,  and  sky,  are 
gradually  diluted  into  each  other,  and  the  colour  of  the 
whole  becomes  more  and  more  uniform.  This  change 
of  appearance,  corresponding  to  the  several  distances, 
marks  the  distance  more  exactly  than  if  the  whole  ob- 
ject had  been  of  one  colour. 

Dr.  Smith,  in  his  "  Optics, "  gives  us  a  very  curious 
observation  made  by  Bishop  Berkeley,  in  his  travels 
through  Italy  and  Sicily.  He  observed,  That,  in  those 
countries,  cities  and  palaces  seen  at  a  great  distance  ap- 
peared nearer  to  him  by  several  miles  than  they  really 
were  :  and  he  very  judiciously  imputed  it  to  this  cause. 
That  the  purity  of  the  Italian  and  Sicilian  air,  gave  to 
very  distant  objects  that  degree  of  brightness  and  dis- 
tinctness which,  in  the  grosser  air  of  his  own  country, 
was  to  be  seen  only  in  those  that  are  near.  The  purity 
of  the  Italian  air  hath  been  assigned  as  the  reason  why 
the  Italian  painters  commonly  give  a  more  lively  colour 
to  the  sky  than  the  Flemish.  Ought  they  not,  for  the 
same  reason,  to  give  less  degradation  of  the  colours,  and 
less  indistinctness  of  the  minute  parts,  in  the  represen- 
tation of  very  distant  objects  ? 

It  is  very  certain  that,  as  in  air  uncommonly  pure,  we 
are  apt  to  think  visible  objects  nearer  and  less  than  they 


SEC.  XXII.]  THE  PHILOSOPHY   OF  REID.  311 

really  are,  so,  in  air  uncommonly  foggy,  we  are  apt  to 
think  them  more  distant  and  larger  than  the  truth. 
Walking  by  the  sea-side  in  a  thick  fog,  I  see  an  object 
which  seems  to  me  to  be  a  man  on  horseback,  and  at 
the  distance  of  about  half  a  mile.  My  companion,  who 
has  better  eyes,  or  is  more  accustomed  to  see  such  ob- 
jects in  such  circumstances,  assures  me  that  it  is  a  sea- 
gull, and  not  a  man  on  horseback.  Upon  a  second 
view,  I  immediately  assent  to  his  opinion ;  and  now  it 
appears  to  me  to  be  a  sea-gull,  and  at  the  distance  only 
of  seventy  or  eighty  yards.  The  mistake  made  on  this 
occasion,  and  the  correction  of  it,  are  both  so  sudden, 
that  we  are  at  a  loss  whether  to  call  them  by  the  name 
of 'judgment,  or  by  that  of  simple  perception. 

It  is  not  worth  while  to  dispute  about  names ;  but  it 
is  evident  that  my  belief,  both  first  and  last,  was  pro- 
duced rather  by  signs  than  by  arguments,  and  that  the 
mind  proceeded  to  the  conclusion  in  both  cases  by  habit, 
and  not  by  ratiocination.  And  the  process  of  the  mind 
seems  to  have  been  this — First,  Not  knowing,  or  not 
minding,  the  effect  of  a  foggy  air  on  the  visible  appear- 
ance of  objects,  the  object  seems  to  me  to  have  that  deg- 
radation of  colour,  and  that  indistinctness  of  the  out- 
line, which  objects  have  at  the  distance  of  half  a  mile  ; 
therefore,  from  the  visible  appearance  as  a  sign,  I  im- 
mediately proceed  to  the  belief  that  the  object  is  half  a 
mile  distant.  Then,  this  distance,  together  with  the 
visible  magnitude,  signify  to  me  the  real  magnitude, 
which,  supposing  the  distance  to  be  half  a  mile,  must 
be  equal  to  that  of  a  man  on  horseback ;  and  the  fig- 
ure, considering  the  indistinctness  of  the  outline,  agrees 
with  that  of  a  man  on  horseback.  Thus  the  deception 
is  brought  about.  But  when  I  am  assured  that  it  is  a 
sea-gull,  the  real  magnitude  of  a  sea-gull,  together  with 
the  visible  magnitude  presented  to  the  eye,  immediately 
suggest  the  distance,  which,  in  this  case,  cannot  be  above 
seventy  or  eighty  yards  :  the  indistinctness  of  the  figure 


312  THE  PHILOSOPHY   OF   REID.  [Cn.  VI. 

likewise  suggests  the  fogginess  of  the  air  as  its  cause  ; 
and  now  the  whole  chain  of  signs,  and  things  signified, 
seems  stronger  and  better  connected  than  it  was  before  ; 
the  half  mile  vanishes  to  eighty  yards  ;  the  man  on  horse- 
back dwindles  to  a  sea-gull  ;  I  get  a  new  perception, 
and  wonder  how  I  got  the  former,  or  what  is  become 
of  it ;  for  it  is  now  so  entirely  gone,  that  I  cannot  re- 
cover it. 

It  ought  to  be  observed  that,  in  order  to  produce 
such  deceptions  from  the  clearness  or  fogginess  of  the 
air,  it  must  be  uncommonly  clear  or  uncommonly  foggy; 
for  we  learn,  from  experience,  to  make  allowance  for 
that  variety  of  constitutions  of  the  air  which  we  have 
been  accustomed  to  observe,  and  of  which  we  are 
aware.  Bishop  Berkeley  therefore  committed  a  mistake, 
when  he  attributed  the  large  appearance  of  the  horizon- 
tal moon  to  the  faintness  of  her  light,  occasioned  by 
its  passing  through  a  larger  tract  of  atmosphere  :*  for  we 
are  so  much  accustomed  to  see  the  moon  in  all  degrees 
of  faintness  and  brightness,  from  the  greatest  to  the  least, 
that  we  learn  to  make  allowance  for  it;  and  do  not 
imagine  her  magnitude  increased  by  the  faintness  of 
her  appearance.  Besides,  it  is  certain  that  the  horizon- 
tal moon  seen  through  a  tube  which  cuts  off  the  view 
of  the  interjacent  ground,  and  of  all  terrestrial  objects, 
loses  all  that  unusual  appearance  of  magnitude. 

4.  We  frequently  perceive  the  distance  of  objects,  by 
means  of  intervening  or  contiguous  objects,  whose  dis- 
tance or  magnitude  is  otherwise  known.  When  I  per- 
ceive certain  fields  or  tracts  of  ground  to  lie  between 
me  and  an  object,  it  is  evident  that  these  may  become 
signs  of  its  distance.  And  although  we  have  no  par- 
ticular information  of  the  dimensions  of  such  fields  or 
tract,  yet  their  similitude  to  others  which  we  know, 
suggests  their  dimensions. 

*  This  explanation  was  not  original  to  Berkeley. — H. 


SEC.  XXII.]  THE  PHILOSOPHY  OF  REID.  313 

We  are  so  much  accustomed  to  measure  with  our  eye 
the  ground  which  we  travel,  and  to  compare  the  judg 
ments  of  distances  formed  by  sight,  with  our  experience 
or  information,  that  we  learn  by  degrees,  in  this  way, 
to  form  a  more  accurate  judgment  of  the  distance  of 
terrestrial  objects,  than  we  could  do  by  any  of  the  means 
before  mentioned.  An  object  placed  upon  the  top  of 
a  high  building,  appears  much  less  than  when  placed 
upon  the  ground,  at  the  same  distance.  When  it  stands 
upon  the  ground,  the  intervening  tract  of  ground  serves 
as  a  sign  of  its  distance ;  and  the  distance,  together 
with  the  visible  magnitude,  serves  as  a  sign  of  its  real 
magnitude.  But  when  the  object  is  placed  on  high,  this 
sign  of  its  distance  is  taken  away  :  the  remaining  signs 
lead  us  to  place  it  at  a  less  distance  :  and  this  less  dis- 
tance, together  with  the  visible  magnitude,  becomes  a 
sign  of  a  less  real  magnitude. 

The  two  first  means  we  have  mentioned,  would  never 
of  themselves  make  a  visible  object  appear  above  a  hun- 
dred and  fifty,  or  two  hundred  feet,  distant ;  because, 
beyond  that  there  is  no  sensible  change,  either  of  the 
conformation  of  the  eyes,  or  of  the  inclination  of  their 
axes.  The  third  mean  is  but  a  vague  and  undetermi- 
nate  sign,  when  applied  to  distances  above  two  or  three 
hundred  feet,  unless  we  know  the  real  colour  and  figure 
of  the  object ;  and  the  fifth  mean,  to  be  afterwards  men- 
tioned, can  only  be  applied  to  objects  which  are  famil- 
iar, or  whose  real  magnitude  is  known.  Hence  it 
follows,  that,  when  unknown  objects,  upon  or  near  the 
surface  of  the  earth,  are  perceived  to  be  at  the  distance 
of  some  miles,  it  is  always  by  this  fourth  mean  that  WQ 
are  led  to  that  conclusion. 

Dr.  Smith  hath  observed,  very  justly,  that  the  known 
distance  of  the  terrestrial  objects  which  terminate  our 
view,  makes  that  part  of  the  sky  which  is  towards  the 
horizon  appear  more  distant  than  that  which  is  towards 
the  zenith.  Hence  it  comes  to  pass,  that  the  apparent 


314  THE  PHILOSOPHY  OF  REID.  [Cn.  VI. 

figure  of  the  sky  is  not  that  of  a  hemisphere,  but  rather 
a  less  segment  of  a  sphere.  And,  hence,  likewise,  it 
comes  to  pass,  that  the  diameter  of  the  sun  or  moon,  or 
the  distance  between  two  fixed  stars,  seen  contiguous  to 
a  hill,  or  to  any  distant  terrestrial  object,  appears  much 
greater  than  when  no  such  object  strikes  the  eye  at  the 
same  time. 

These  observations  have  heen  sufficiently  explained 
and  confirmed  by  Dr.  Smith.  I  beg  leave  to  add,  that, 
when  the  visible  horizon  is  terminated  by  very  distant 
objects,  the  celestial  vault  seems  to  be  enlarged  in  all  its 
dimensions.  When  I  view  it  from  a  confined  street  or 
lane,  it  bears  some  proportion  to  the  buildings  that  sur- 
round me ;  but,  when  I  view  it  from  a  large  plain,  ter- 
minated on  all  hands  by  hills  which  rise  one  above 
another  to  the  distance  of  twenty  miles  from  the  eye, 
methinks  I  see  a  new  heaven,  whose  magnificence  de- 
clares the  greatness  of  its  Author,  and  puts  every  human 
edifice  out  of  countenance  ;  for  now  the  lofty  spires  and 
the  gorgeous  palaces  shrink  into  nothing  before  it,  and 
bear  no  more  proportion  to  the  celestial  dome  than  their 
makers  bear  to  its  Maker. 

5.  There  remains  another  mean  by  which  we  perceive 
the  distance  of  visible  objects — and  that  is  the  diminu- 
tion of  their  visible  or  apparent  magnitude.  By  experi- 
ence, I  know  what  figure  a  man,  or  any  other  known 
object,  makes  to  my  eye  at  the  distance  of  ten  feet — I 
perceive  the  gradual  and  proportional  diminution  of  this 
visible  figure,  at  the  distance  of  twenty,  forty,  a  hundred 
feet,  and  at  greater  distances,  until  it  vanish  altogether. 
Hence  a  certain  visible  magnitude  of  a  known  object 
becomes  the  sign  of  a  certain  determinate  distance,  and 
carries  along  with  it  the  conception  and  belief  of  that 
distance. 

In  this  process  of  the  mind,  the  sign  is  not  a  sensation  ; 
it  is  an  original  perception.  We  perceive  the  visible  fig- 
ure and  visible  magnitude  of  the  object,  by  the  original 


SEC.  XXII.]  THE  PHILOSOPHY  Of  REID.  315 

powers  of  vision  ;  but  the  visible  figure  is  used  only  as 
a  sign  of  the  real  figure,  and  the  visible  magnitude  is 
used  only  as  a  sign  either  of  the  distance,  or  of  the  real 
magnitude,  of  the  object :  and,  therefore,  these  original 
perceptions,  like  other  mere  signs,  pass  through  the  mind 
without  any  attention  or  reflection. 

This  last  mean  of  perceiving  the  distance  of  known 
objects,  serves  to  explain  some  very  remarkable  phse- 
nomena  in  optics,  which  would  otherwise  appear  very 
mysterious.  When  we  view  objects  of  known  dimen- 
sions through  optical  glasses,  there  is  no  other  mean  left 
of  determining  their  distance,  but  this  fifth.  Hence  it 
follows,  that  known  objects  seen  through  glasses,  must 
seem  to  be  brought  nearer,  in  proportion  to  the  magni- 
fying power  of  the  glass,  or  to  be  removed  to  a  greater 
distance  in  proportion  to  the  diminishing  power  of  the 
glass. 

If  a  man  who  had  never  before  seen  objects  through  a 
telescope,  were  told  that  the  telescope,  which  he  is  about 
to  use,  magnifies  the  diameter  of  the  object  ten  times ; 
when  he  looks  through  this  telescope  at  a  man  six  feet 
high,  what  would  he  expect  to  see  ?  Surely  he  would 
very  naturally  expect  to  see  a  giant  sixty  feet  high.  But 
he  sees  no  such  thing.  The  man  appears  no  more  than 
six  feet  high,  and  consequently  no  bigger  than  he  really 
is ;  but  he  appears  ten  times  nearer  than  he  is.  The 
telescope  indeed  magnifies  the  image  of  this  man  upon 
the  retina  ten  times  in  diameter,  and  must,  therefore, 
magnify  his  visible  figure  in  the  same  proportion;  and, 
as  we  have  been  accustomed  to  see  him  of  this  visible 
magnitude  when  he  was  ten  times  nearer  than  he  is  pres- 
ently, and  in  no  other  case,  this  visible  magnitude,  there- 
fore, suggests  the  conception  and  belief  of  that  distance 
of  the  object  with  which  it  hath  been  always  connected. 
We  have  been  accustomed  to  conceive  this  amplification 
of  the  visible  figure  of  a  known  object,  only  as  the  effect 
or  sign  of  its  being  brought  nearer  :  and  we  have  annexed 


3r6  THE  PHILOSOPHY  OF  REID.  [Cn.  VI. 

a  certain  determinate  distance  to  every  degree  of  visible 
magnitude  of  the  object ;  and,  therefore,  any  particular 
degree  of  visible  magnitude,  whether  seen  by  the  naked 
eye  or  by  glasses,  brings  along  with  it  the  conception 
and  belief  of  the  distance  which  corresponds  to  it  This 
is  the  reason  why  a  telescope  seems  not  to  magnify 
known  objects,  but  to  bring  them  nearer  to  the  eye. 

When  we  look  through  a  pin-hole,  or  a  single  micro- 
scope, at  an  object  which  is  half  an  inch  from  the  eye, 
the  picture  of  the  object  upon  the  retina  is  not  enlarged, 
but  only  rendered  distinct ;  neither  is  the  visible  figure 
enlarged  :  yet  the  object  appears  to  the  eye  twelve  or 
fourteen  times  more  distant,  and  as  many  times  larger  in 
diameter,  than  it  really  is.  Such  a  telescope  as  we  have 
mentioned  amplifies  the  image  on  the  retina,  and  the 
visible  figure  of  the  object,  ten  times  in  diameter,  and 
yet  makes  it  seem  no  bigger,  but  only  ten  times  nearer. 
These  appearances  had  been  long  observed  by  the  writers 
on  topics ;  they  tortured  their  invention  to  find  the 
causes  of  them  from  optical  principles ;  but  in  vain  : 
they  must  be  resolved  into  habits  of  perception,  which 
are  acquired  by  custom,  but  are  apt  to  be  mistaken  for 
original  perceptions.  The  Bishop  of  Cloyne  first  fur- 
nished the  world  with  the  proper  key  for  opening  up 
these  mysterious  appearances  ;  but  he  made  considerable 
mistakes  in  the  application  of  it.  Dr.  Smith,  in  his 
elaborate  and  judicious  treatise  of  ' '  Optics,"  hath  applied 
it  to  the  apparent  distance  of  objects  seen  with  glasses, 
and  to  the  apparent  figure  of  the  heavens,  with  such 
happy  success,  that  there  can  be  no  more  doubt  about 
the  causes  of  these  phenomena. 

Section  XXIII. 

OF   THE    SIGNS    USED    IN   OTHER   ACQUIRED    PERCEPTIONS. 

The  distance  of  objects  from  the  eye  is  the  most  im- 
portant lesson  in  vision.  Many  others  are  easily  learned 


SEC.  XXIII.]  THE  PHILOSOPHY  OF  REID.  317 

in  consequence  of  it.  The  distance  of  the  object,  joined 
with  its  visible  magnitude,  is  a  sign  of  its  real  magni- 
tude :  and  the  distance  of  the  several  parts  of  an  object, 
joined  with  its  visible  figure,  becomes  a  sign  of  its  real 
figure.  Thus,  when  I  look  at  a  globe  which  stands  be- 
fore me,  by  the  original  powers  of  sight  I  perceive  only 
something  of  a  circular  form,  variously  coloured.  The 
visible  figure  hath  no  distance  from  the  eye,  no  convexity, 
nor  hath  it  three  dimensions  ;  even  its  length  and  breadth 
are  incapable  of  being  measured  by  inches,  feet,  or  other 
linear  measures.  But,  when  I  have  learned  to  perceive 
the  distance  of  every  part  of  this  object  from  the  eye, 
this  perception  gives  it  convexity,  and  a  spherical  figure  ; 
and  adds  a  third  dimension  to  that  which  had  but  two 
before.  The  distance  of  the  whole  object  makes  me 
likewise  perceive  the  real  magnitude ;  for,  being  accus- 
tomed to  observe  how  an  inch  or  a  foot  of  length  affects 
the  eye  at  that  distance,  I  plainly  perceive  by  my  eye 
the  linear  dimensions  of  the  globe,  and  can  affirm  with 
certainty  that  its  diameter  is  about  one  foot  and  three 
inches. 

It  was  shewn  in  the  yth  section  of  this  chapter  that 
the  visible  figure  of  a  body  may,  by  mathematical  rea- 
soning, be  inferred  from  its  real  figure,  distance,  and 
position, ; with  regard  to  the  eye:  in  like  manner,  we 
may,  by  mathematical  reasoning,  from  the  visible  figure, 
together  with  the  distance  of  the  several  parts  of  it  from 
the  eye,  infer  the  real  figure  and  position.  But  this  last 
inference  is  not  commonly  made  by  mathematical  rea- 
soning, nor,  indeed,  by  reasoning  of  any  kind,  but  by 
custom. 

The  original  appearance  which  the  colour  of  an  object 
makes  to  the  eye,  is  a  sensation  for  which  we  have  no 
name,  because  it  is  used  merely  as  a  sign,  and  is  never 
made  an  object  of  attention  in  common  life  :  but  this 
appearance,  according  to  the  different  circumstances, 
signifies  various  things.  If  a  piece  of  cloth,  of  one  uni- 


318  THE  PHILOSOPHY  OF  REID.  [Cn.  VI. 

form  colour,  is  laid  so  that  part  of  it  is  in  the  sun,  and 
part  in  the  shade,  the  appearance  of  colour,  in  these  dif- 
ferent parts,  is  very  different :  yet  we  perceive  the  colour 
to  be  the  same  ;  we  interpret  the  variety  of  appearance 
as  a  sign  of  light  and  shade,  and  not  as  a  sign  of  real 
difference  in  colour.  But,  if  the  eye  could  be  so  far  de- 
ceived as  not  to  perceive  the  difference  of  light  in  the 
two  parts  of  the  cloth,  we  should,  in  that  case,  interpret 
the  variety  of  appearance  to  signify  a  variety  of  colour  in 
the  parts  of  the  cloth. 

Again,  if  we  suppose  a  piece  of  cloth  placed  as  before, 
but  having  the  shaded  part  so  much  brighter  in  the 
colour  that  it  gives  the  same  appearance  to  the  eye  as 
the  more  enlightened  part,  the  sameness  of  appearance 
will  here  be  interpreted  to  signify  a  variety  of  colour, 
because  we  shall  make  allowance  for  the  effect  of  light 
and  shade. 

When  the  real  colour  of  an  object  is  known,  the  ap- 
pearance of  it  indicates,  in  some  circumstances,  the  de- 
gree of  light  or  shade  ;  in  others,  the  colour  of  the  cir- 
cumambient bodies,  whose  rays  are  reflected  by  it;  and, 
in  other  circumstances,  it  indicates  the  distance  or 
proximity  of  the  object — as  was  observed  in  the  last  sec- 
tion ;  and  by  means  of  these,  many  other  things  are  sug- 
gested1 to  the  mind.  Thus,  an  unusual  appearance  in 
the  colour  of  familiar  objects  may  be  the  diagnostic  of  a 
disease  in  the  spectator.  The  appearance  of  things  in 
my  room  may  indicate  sunshine  or  cloudy  weather,  the 
earth  covered  with  snow  or  blackened  with  rain.  It 
hath  been  observed,  that  the  colour  of  the  sky,  in  a 
piece  of  painting,  may  indicate  the  country  of  the 
painter,  because  the  Italian  sky  is  really  of  a  different 
colour  from  the  Flemish. 

It  was  already  observed,  that  the  original  and  acquired 
perceptions  which  we  have  by  our  senses,  are  the  lan- 
guage of  nature  to  man,  which,  in  many  respects,  hath 
a  great  affinity  to  human  languages.  The  instances 


SEC.  XXIII.]  THE  PHILOSOPHY  OF  REID.  319 

which  we  have  given  of  acquired  perceptions,  suggest 
this  affinity — that,  as,  in  human  languages,  ambiguities 
are  often  found,  so  this  language  of  nature  in  our  ac- 
quired perceptions  is  not  exempted  from  them.  We 
have  seen,  in  vision  particularly,  that  the  same  appear- 
ance to  the  eye,  may,  in  different  circumstances,  indicate 
different  things.  Therefore,  when  the  circumstances  are 
unknown  upon  which  the  interpretation  of  the  signs  de- 
pends, their  meaning  must  be  ambiguous ;  and  when 
the  circumstances  are  mistaken,  the  meaning  of  the  signs 
must  also  be  mistaken. 

This  is  the  case  in  all  the  phaenomena  which  we  call 
fallacies  of  the  senses ;  and  particularly  in  those  which 
are  called  fallacies  in  vision.  The  appearance  of  things 
to  the  eye  always  corresponds  to  the  fixed  laws  of  Na- 
ture ;  therefore,  if  we  speak  properly,  there  is  no  fallacy 
in  the  senses.  Nature  always  speaketh  the  same  lan- 
guage, and  useth  the  same  signs  in  the  same  circum- 
stances ;  but  we  sometimes  mistake  the  meaning  of  th( 
signs,  either  through  ignorance  of  the  laws  of  Nature,  or 
through  ignorance  of  the  circumstances  which  attend  the 
signs. 

To  a  man  unacquainted  with  the  principles  of  op- 
tics, almost  every  experiment  that  is  made  with  the 
prism,  with  the  magic  lanthorn,  with  the  telescope,  with 
the  microscope,  seems  to  produce  some  fallacy  in  vision. 
Even  the  appearance  of  a  common  mirror,  to  one  alto- 
gether unacquainted  with  the  effects  of  it,  would  seem 
most  remarkably  fallacious.  For  how  can  a  man  be 
more  imposed  upon,  than  in  seeing  that  before  him 
which  is  really  behind  him  ?  How  can  he  be  more  im- 
posed upon,  than  in  being  made  to  see  himself  several 
yards  removed  from  himself?  Yet  children,  even  before 
they  can  speak  their  mother  tongue,  learn  not  to  be  de- 
ceived by  these  appearances.  These,  as  well  as  all  the 
other  surprising  appearances  produced  by  optical  glasses, 
are  a  part  of  the  visual  language,  and,  to  those  who  un- 


320  THE  PHILOSOPHY  OF  REID.  [CH.  VI. 

derstand  the  laws  of  Nature  concerning  light  and  col- 
ours, are  in  nowise  fallacious,  but  have  a  distinct  and 
true  meaning. 

Section  XXIV. 

OF   THE    ANALOGY    BETWEEN    PERCEPTION     AND     THE     CREDIT 
WE    GIVE    TO    HUMAN    TESTIMONY. 

The  objects  of  human  knowledge  are  innumerable  ; 
but  the  channels  by  which  it  is  conveyed  to  the  mind 
are  few.  Among  these,  the  perception  of  external  things 
by  our  senses,  and  the  informations  which  we  receive 
upon  human  testimony,  are  not  the  least  considerable  ; 
and  so  remarkable  is  the  analogy  between  these  two,  and 
the  analogy  between  the  principles  of  the  mind  which 
are  subservient  to  the  one  and  those  which  are  subservi- 
ent to  the  other,  that,  without  further  apology,  we  shall 
consider  them  together. 

In  the  testimony  of  Nature  given  by  the  senses,  as  well 
as  in  human  testimony  given  by  language,  things  are 
/  signified  to  us  by  signs  :  and  in  one  as  well  as  the  other, 
the  mind,  either  by  original  principles  or  by  custom, 
passes  from  the  sign  to  the  conception  and  belief  of  the 
things  signified. 

We  have  distinguished  our  perceptions  into  original 
and  acquired  ;  and  language,  into  natural  and  artificial. 
Between  acquired  perception  and  artificial  language, 
there  is  a  great  analogy  ;  but  still  a  greater  between  orig- 
inal perception  and  natural  language. 

The  signs  in  original  perception  are  sensations,  of 
which  Nature  hath  given  us  a  great  variety,  suited  to  the 
variety  of  the  things  signified  by  them.  Nature  hath 
established  a  real  connection  between  the  signs  and  the 
things  signified;  and  Nature  hath  also  taught  us  the 
interpretation  of  the  signs — so  that,  previous  to  ex- 
perience, the  sign  suggests  the  thing  signified,  and  creates 
the  belief  of  it. 


SEC.  XXIV.]  THE  PHILOSOPHY  OF   REID.  $21 

The  signs  in  natural  language  are  features  of  the  face, 
gestures  of  the  body,  and  modulations  of  the  voice;  the 
variety  of  which  is  suited  to  the  variety  of  the  things 
signified  by  them.  Nature  hath  established  a  real  con- 
nection between  these  signs,  and  the  thoughts  and  dis- 
positions of  the  mind  which  are  signified  by  them;  and 
Nature  hath  taught  us  the  interpretation  of  these  signs;  so 
that,  previous  to  experience,  the  signs  suggest  the  thing 
signified,  and  create  the  belief  of  it. 

A  man  in  company,  without  doing  good  or  evil,  with- 
out uttering  an  articulate  sound,  may  behave  himself 
gracefully,  civilly,  politely;  or,  on  the  contrary,  meanly, 
rudely,  and  impertinently.  We  see  the  dispositions  of 
his  mind  by  their  natural  signs  in  his  countenance  and 
behavior,  in  the  same  manner  as  we  perceive  the  figure 
and  other  qualities  of  bodies  by  the  sensations  which 
nature  hath  connected  with  them. 

The  signs  in  the  natural  language  of  the  human 
countenance  and  behaviour,  as  well  as  the  signs  in  our 
original  perceptions,  have  the  same  signification  in  all 
climates  and  in  all  nations;  and  the  skill  of  interpreting 
them  is  not  acquired,  but  innate. 

In  acquired  perception,  the  signs  are  either  sensations, 
or  things  which  we  perceive  by  means  of  sensations. 
The  connection  between  the  sign  and  the  thing  signified, 
is  established  by  nature;  and  we  discover  this  connection 
by  experience;  but  not  without  the  aid  of  our  original 
perceptions,  or  of  those  which  we  have  already  acquired. 
After  this  connection  is  discovered,  the  sign,  in  like 
manner  as  in  original  perception,  always  suggests  the 
thing  signified,  and  creates  the  belief  of  it. 

In  artificial  language,  the  signs  are  articulate  sounds, 
whose  connection  with  the  things  signified  by  them,  is 
established  by  the  will  of  men;  and,  in  learning  our 
mother  tongue,  we  discover  this  connection  by  experience; 
but  not  without  the  aid  of  natural  language,  or  of  what 
we  had  before  attained  of  artificial  language.  And.  after 


322  THE  PHILOSOPHY  OF  REID.  [Cn.  VI. 

this  connection  is  discovered,  the  sign,  as  in  natural 
language,  always  suggests  the  thing  signified,  and  creates 
the  belief  of  it. 

Our  original  perceptions  are  few,  compared  with  the 
acquired;  but,  without  the  former,  we  could  not  possibly 
attain  the  latter.  In  like  manner,  natural  language  is 
scanty,  compared  with  artificial;  but,  without  the  former 
we  could  not  possibly  attain  the  latter. 

Our  original  perceptions,  as  well  as  the  natural 
language  of  human  features  and  gestures,  must  be 
resolved  into  particular  principles  of  the  human  con- 
stitution. Thus,  it  is  by  one  particular  principle  of  our 
constitution  that  certain  features  express  anger;  and,  by 
another  particular  principle,  that  certain  features  express 
benevolence.  It  is,  in  like  manner,  by  one  particular 
principle  of  our  constitution  that  a  certain  sensation 
signifies  hardness  in  the  body  which  I  handle;  and  it  is 
by  another  particular  principle  that  a  certain  sensation 
signifies  motion  in  that  body. 

But  our  acquired  perceptions,  and  the  information  we 
receive  by  means  of  artificial  language,  must  be  resolved 
into  general  principles  of  the  human  constitution.  When 
a  painter  perceives  that  this  picture  is  the  work  of 
Raphael,  that  the  work  of  Titian;  a  jeweller,  that  this  is 
a  true  diamond,  that  a  counterfeit;  a  sailor,  that  this  is  a 
ship  of  five  hundred  ton,  that  of  four  hundred;  these  dif- 
ferent acquired  perceptions  are  produced  by  the  same 
general  principles  of  the  human  mind,  which  have  a  dif- 
ferent operation  in  the  same  person,  according  as  they  are 
variously  applied,  and  in  different  persons  according  to 
the  diversity  of  their  education  and  manner  of  life.  In 
like  manner,  when  certain  articulate  sounds  convey  to 
my  mind  the  knowledge  of  the  battle  of  Pharsalia,  and 
others,  the  knowledge  of  the  battle  of  Poltowa — when  a 
Frenchman  and  an  Englishman  receive  the  same  in- 
formation by  different  articulate  sounds — the  signs  used 
in  these  different  cases,  produce  the  knowledge  and  belief 


SEC.  XXIV.]  THE  PHILOSOPHY  OF  REID.  323 

of  the  things  signified,  by  means  of  the  same  general 
principles  of  the  human  constitution. 

Now,  if  we  compare  the  general  principles  of  our  con- 
stitution, which  fit  us  for  receiving  information  from  our 
fellow-creatures  by  language,  with  the  general  principles 
which  fit  us  for  acquiring  the  perception  of  things  by  our 
senses,  we  shall  find  them  to  be  very  similar  in  their 
nature  and  manner  of  operation. 

When  we  begin  to  learn  our  mother  tongue,  we  per- 
ceive, by  the  help  of  natural  language,  that  they  who 
speak  to  us  use  certain  sounds  to  express  certain  things, 
we  imitate  the  same  sounds  when  we  would  express  the 
same  things;  and  find  that  we  are  understood. 

But  here  a  difficulty  occurs  which  merits  our  attention, 
because  the  solution  of  it  leads  to  some  original  principles 
of  the  human  mind,  which  are  of  great  importance,  and 
of  very  extensive  influence.  We  know  by  experience 
that  men  have  used  such  words  to  express  such  things; 
but  all  experience  is  of  the  past,  and  can,  of  itself,  give 
no  notion  or  belief  of  what  is  future.  How  come  we, 
then,  to  believe,  and  to  rely  upon  it  with  assurance,  that 
men,  who  have  it  in  their  power  to  do  otherwise,  will 
continue  to  use  the  same  words  when  they  think  the  same 
things  ?  Whence  comes  this  knowledge  and  belief — this 
foresight,  we  ought  rather  to  call  it — of  the  future  and 
voluntary  actions  of  our  fellow-creatures  ?  Have  they 
promised  that  they  will  never  impose  upon  us  by 
equivocation  or  falsehood  ?  No,  they  have  not.  And, 
if  they  had,  this  would  not  solve  the  difficulty;  for  such 
promise  must  be  expressed  by  words  or  by  other  signs; 
and,  before  we  can  rely  upon  it,  we  must  be  assured 
that  they  put  the  usual  meaning  upon  the  signs  which 
express  that  promise.  No  man  of  common  sense  ever 
thought  of  taking  a  man's  own  word  for  his  honesty;  and 
it  is  evident  that  we  take  his  veracity  for  granted  when 
we  lay  any  stress  upon  his  word  or  promise.  I  might 
add,  that  this  reliance  upon  the  declarations  and  testimony 


324  THE  PHILOSOPHY  OF  REID.  [Cn.VI. 

of  men  is  found  in  children  long  before  they  Know  what 
a  promise  is. 

There  is,  therefore,  in  the  human  mind  an  early 
anticipation,  neither  derived  from  experience,  nor  from 
reason,  nor  from  any  compact  or  promise,  that  our  fel- 
low-creatures will  use  the  same  signs  in  language,  when 
they  have  the  same  sentiments. 

This  is,  in  reality,  a  kind  of  prescience  of  human 
actions;  and  it  seems  to  me  to  be  an  original  principle  of 
the  human  constitution,  without  which  we  should  be 
incapable  of  language,  and  consequently  incapable  of 
instruction. 

The  wise  and  beneficent  Author  of  Nature,  who  in- 
tended that  we  should  be  social  creatures,  and  that  we 
should  receive  the  greatest  and  most  important  part  of 
our  knowledge  by  the  information  of  others,  hath,  for 
these  purposes,  implanted  in  our  natures  two  principles 
that  tally  with  each  other. 

The  first  of  these  principles  is,  a  propensity  to  speak 
truth,  and  to  use  the  signs  of  language  so  as  to  convey 
our  real  sentiments.  This  principle  has  a  powerful 
operation,  even  in  the  greatest  liars;  for,  where  they  lie 
once,  they  speak  truth  a  hundred  times.  Truth  is  always 
uppermost,  and  is  the  natural  issue  of  the  mind.  It 
requires  no  art  or  training,  no  inducement  or  temptation, 
but  only  that  we  yield  to  a  natural  impulse.  Lying,  on 
the  contrary,  is  doing  violence  to  our  nature;  and  is  never 
practised,  even  by  the  worst  men,  without  some  tempta- 
tion. Speaking  truth  is  like  using  our  natural  food, 
which  we  would  do  from  appetite,  although  it  answered 
no  end;  but  lying  is  like  taking  physic,  which  is  nauseous 
to  the  taste,  and  which  no  man  takes  but  for  some  end 
which  he  cannot  otherwise  attain. 

If  it  should  be  objected,  That  men  may  be  influenced 
by  moral  or  political  considerations  to  speak  truth,  and, 
therefore,  that  their  doing  so  is  no  proof  of  such  an 
original  principle  as  we  have  mentiond — I  answer,  First, 


SEC.  XXIV.)  THE  PHILOSOPHY  OF  REID.  325 

That  moral  or  political  considerations  can  have  no 
influence  until  we  arrive  at  years  of  understanding  and 
reflection;  and  it  is  certain,  from  experience,  that  children 
keep  to  truth  invariably,  before  they  are  capable  of  being 
influenced  by  such  considerations.  Secondly,  When  we 
are  influenced  by  moral  or  political  considerations,  we 
must  be  conscious  of  that  influence,  and  capable  of  per- 
ceiving it  upon  reflection.  Now,  when  I  reflect  upon  my 
actions  most  attentively,  I  am  not  conscious  that,  in 
speaking  truth,  I  am  influenced  on  ordinary  occasions  by 
any  motive,  moral  or  political.  I  find  that  truth  is  always 
at  the  door  of  my  lips,  and  goes  forth  spontaneously,  if 
not  held  back.  It  requires  neither  good  nor  bad  intention 
to  bring  it  forth,  but  only  that  I  be  artless  and  undesign- 
ing.  There  may  indeed  be  temptations  to  falsehood, 
which  would  be  too  strong  for  the  natural  principle  of 
veracity,  unaided  by  principles  of  honor  or  virtue;  but 
where  there  is  no  such  temptation,  we  speak  truth  by 
instinct — and  this  instinct  is  the  principle  I  have  been 
explaining. 

By  this  instinct,  a  real  connection  is  formed  between 
our  words  and  our  thoughts,  and  thereby  the  former 
became  fit  to  be  signs  of  the  latter,  which  they  could  not 
otherwise  be.  And  although  this  connection  is  broken 
in  every  instance  of  lying  and  equivocation,  yet  these 
instances  being  comparatively  few,  the  authority  of  human 
testimony  is  only  weakened  by  them,  but  not  destroyed. 

Another  original  principle  implanted  in  us  by  the 
Supreme  Being,  is  a  disposition  to  confide  in  the  veracity 
of  others,  and  to  believe  what  they  tell  us.  This  is  the 
counterpart  to  the  former;  and,  as  that  may  be  called  the 
principle  of  veracity,  we  shall,  for  want  of  a  more  proper 
name,  call  this  the  principle  of  credulity.  It  is  unlimited 
in  children,  until  they  meet  with  instances  of  deceit  and 
falsehood;  and  it  retains  a  very  considerable  degree  of 
strength  through  life. 

If  Nature  had  left  the  mind  of  the  speaker  in  (equilibria, 


326  THE  PHILOSOPHY  OF  REID.  [Cn.  VI. 

without  any  inclination  to  the  side  of  truth  more  than  to 
that  of  falsehood,  children  would  lie  as  often  as  they 
speak  truth,  until  reason  was  so  far  ripened  as  to  suggest 
the  imprudence  of  lying,  or  conscience,  as  to  suggest  its 
immorality.  And  if  Nature  had  left  the  mind  of  the  hearer 
in  cequilibrio,  without  any  inclination  to  the  side  of  belief 
more  than  to  that  of  disbelief,  we  should  take  no  man's 
word  until  we  had  positive  evidence  that  he  spoke  truth. 
His  testimony  would,  in  this  case,  have  no  more  authority 
than  his  dreams;  which  may  be  true  or  false,  but  no  man 
is  disposed  to  believe  them,  on  this  account,  that  they 
were  dreamed.  It  is  evident  that,  in  the  matter  of 
testimony,  the  balance  of  human  judgment  is  by  nature 
inclined  to  the  side  of  belief;  and  turns  to  that  side  of 
itself,  when  there  is  nothing  put  into  the  opposite  scale. 
If  it  was  not  so,  no  proposition  that  is  uttered  in  dis- 
course would  be  believed,  until  it  was  examined  and  tried 
by  reason;  and  most  men  would  be  unable  to  find  reasons 
for  believing  the  thousandth  part  of  what  is  told  them. 
Such  distrust  and  incredulity  would  deprive  us  of  the 
greatest  benefits  of  society,  and  place  us  in  a  worse  con- 
dition than  that  of  savages. 

Children,  on  this  supposition,  would  be  absolutely  in- 
credulous, and,  therefore,  absolutely  incapable  of  in- 
struction: those  who  had  little  knowledge  of  human  life, 
and  of  the  manners  and  characters  of  men,  would  be  in 
the  next  degree  incredulous:  and  the  most  credulous 
men  would  be  those  of  greatest  experience,  and  of 
the  deepest  penetration;  because,  in  many  cases,  they 
would  be  able  to  find  good  reasons  for  believing  tes- 
timony, which  the  weak  and  the  ignorant  could  not 
discover. 

In  a  word,  if  credulity  were  the  effect  of  reasoning 
and  experience,  it  must  grow  up  and  gather  strength,  in 
the  same  proportion  as  reason  and  experience  do.  But, 
if  it  is  the  gift  of  Nature,  it  will  be  strongest  in  childhood, 
and  limited  and  restrained  by  experience;  and  the  most 


SEC.  XXIV.]  THE  PHILOSOPHY  OF  REID.  327 

superficial  view  of  human  life  shews,  that  the  last  is 
really  the  case,  and  not  the  first* 

It  is  the  intention  of  Nature,  that  we  should  be  car- 
ried in  arms  before  we  are  able  to  walk  upon  our  legs; 
and  it  is  likewise  the  intention  of  Nature,  that  our  belief 
should  be  guided  by  the  authority  and  reason  of  others, 
before  it  can  be  guided  by  our  own  reason.  The  weak- 
ness of  the  infant,  and  the  natural  affection  of  the  mother, 
plainly  indicate  the  former;  and  the  natural  credulity  of 
youth,  and  authority  of  age,  as  plainly  indicate  the  lat- 
ter. The  infant,  by  proper  nursing  and  care,  acquires 
strength  to  walk  without  support.  Reason  hath  likewise 
her  infancy,  when  she  must  be  carried  in  arms:  then  she 
leans  entirely  upon  authority,  by  natural  instinct,  as  if 
she  was  conscious  of  her  own  weakness;  and,  without 
this  support,  she  becomes  vertiginous.  When  brought 
to  maturity  by  proper  culture,  she  begins  to  feel  her  own 
strength,  and  leans  less  upon  the  reason  of  others:  she 
learns  to  suspect  testimony  in  some  cases,  and  to  dis- 
believe it  in  others;  and  sets  bounds  to  that  authority  to 
which  she  was  at  first  entirely  subject.  But  still,  to  the 
end  of  life,  she  finds  a  necessity  of  borrowing  light  from 
testimony,  where  she  has  none  within  herself,  and  of 
leaning,  in  some  degree,  upon  ~the  reason  of  others, 
where  she  is  conscious  of  her  own  imbecility. 

And  as,  in  many  instances,  Reason,  even  in  her  ma- 
turity, borrows  aid  from  testimony,  so  in  others  she  mu- 
tually gives  aid  to  it,  and  strengthens  its  authority. 
For,  as  we  find  good  reason  to  reject  testimony  in  some 
cases,  so  in  others  we  find  good  reason  to  reply  upon  it 
with  perfect  security,  in  our  most  important  concerns. 
The  character,  the  number,  and  the  disinterestedness  of 
witnesses,  the  impossibility  of  collusion,  and  the  incredi- 
bility of  their  concurring  in  their  testimony  without  col- 


*See,  contra,   Priestley's   "Examination,"    p.  8$.     "Brown's, 
Lect."  lect.  Ixxxiv, 


328  THE  PHILOSOPHY  OF  REID.  [Cn.  VI. 

lusion,  may  give  an  irresistible  strength  to  testimony, 
compared  to  which  its  native  and  intrinsic  authority  is 
very  inconsiderable. 

Having  now  considered  the  general  principles  of  the 
human  mind  which  fit  us  for  receiving  information  from 
our  fellow-creatures,  by  the  means  of  language,  let  us 
next  consider  the  general  principles  which  fit  us  for  re- 
ceiving the  information  of  Nature  by  our  acquired  per- 
ceptions. 

It  is  undeniable,  and  indeed  is  acknowledged  by  all, 
that  when  we  have  found  two  things  to  have  been  con- 
stantly conjoined  in  the  course  of  nature,  the  appearance 
of  one  of  them  is  immediately  followed  by  the  conception 
and  belief  of  the  other.  The  former  becomes  a  natural 
sign  of  the  latter;  and  the  knowledge  of  their  constant 
conjunction  in  time  past,  whether  got  by  experience  or 
otherwise,  is  sufficient  to  make  us  rely  with  assurance 
upon  the  continuance  of  that  conjunction. 

This  process  of  the  human  mind  is  so  familiar  that  we 
never  think  of  inquiring  into  the  principles  upon  which 
it  is  founded.  We  are  apt  to  conceive  it  as  a  self-evi- 
dent truth,  that  what  is  to  come  must  be  similar  to  what 
is  past.  Thus,  if  a  certain  degree  of  cold  freezes  water 
to-day,  and  has  been  known  to  do  so  in  all  time  past,  we 
have  no  doubt  but  the  same  degree  of  cold  will  freeze 
water  to-morrow,  or  a  year  hence.  That  this  is  a  truth 
which  all  men  believe  as  soon  as  they  understand  it,  I 
readily  admit;  but  the  question  is,  Whence  does  its  evi- 
dence arise?  Not  from  comparing  the  ideas,  surely. 
For,  when  I  compare  the  idea  of  cold  with  that  of  water 
hardened  into  a  transparent  solid  body,  I  can  perceive 
no  connection  between  them:  no  man  can  shew  the  one 
to  be  the  necessary  effect  of  the  other;  no  man  can  give 
a  shadow  of  reason  why  Nature  hath  conjoined  them. 
But  do  we  not  learn  their  conjunction  from  experience  ? 
True;  experience  informs  us  that  they  have  been  con- 
j  oined  in  time  past;  but  no  man  ever  had  any  experience 


Sac.  XXIV.)  THE  PHILOSOPHY  OF  REID.  329 

of  what  is  future:  and  this  is  the  very  question  to  be  re- 
solved, How  we  come  to  believe  that  the  future  will  be 
like  the/tfj//3  Hath  the  Author  of  nature  promised  this  ? 
Or  were  we  admitted  to  his  council,  when  he  established 
the  present  laws  of  nature,  and  determined  the  time  of 
their  continuance.  No,  surely.  Indeed,  if  we  believe 
that  there  is  a  wise  and  good  Author  of  nature,  we  may 
see  a  good  reason  why  he  should  continue  the  same  laws 
of  nature,  and  the  same  connections  of  things,  for  a  long 
time:  because,  if  he  did  otherwise,  we  could  learn  noth- 
ing from  what  is  past,  and  all  our  experience  would  be 
of  no  use  to  us.  But,  though  this  consideration,  when 
we  come  to  the  use  of  reason,  may  confirm  our  belief  of 
the  continuance  of  the  present  course  of  nature,  it  is  cer- 
tain that  it  did  not  give  rise  to  this  belief;  for  children 
and  idiots  have  this  belief  as  soon  as  they  know  that  fire 
will  burn  them.  It  must,  therefore,  be  the  effect  of  in- 
stinct, not  of  reason.  * 

The  wise  Author  of  our  nature  intended,  that  a  great 
and  necessary  part  of  our  knowledge  should  be  derived 
from  experience,  before  we  are  capable  of  reasoning,  and 
he  hath  provided  means  perfectly  adequate  to  this  inten- 
tion. For,  First,  He  governs  nature  by  fixed  laws,  so 
that  we  find  innumerable  connections  of  things  which 
continue  from  age  to  age.  Without  this  stability  of  the 
course  of  nature,  there  could  be  no  experience;  or,  it 
would  be  a  false  guide,  and  lead  us  into  error  and  mis- 
chief. If  there  were  not  a  principle  of  veracity  in  the 
human  mind,  men's  words  would  not  be  signs  of  their 
thoughts:  and  if  there  were  no  regularity  in  the  course 
of  nature,  no  one  thing  could  be  a  natural  sign  of  an- 
other. Secondly,  He  hath  implanted  in  human  minds 

*  Compare  Stewart's  "Elements,"  vol.  I.,  chap.  iv.  §  5,  p.  205, 
sixth  edition ;  "Philosophical  Essays,"  p.  74,  sqq.,  fourth  edition; 
Royer  Collard,  in  Jouffroy's  " Oeuvres  de  Reid,"  t.  IV.  p.  279,  sqq. ; 
with  Priestley's  "Examination,"  p.  86.  sqq.  I  merely  refer  to 
works  relative  to  Reid's  doctrine. — H. 


330  THE  PHILOSOPHY  OF  REID.  [CH.  VI. 

an  original  principle  by  which  we  believe  and  expect  the 
continuance  of  the  course  of  nature,  and  the  continuance 
of  those  connections  which  we  have  observed  in  time 
past.  It  is  by  this  general  principle  of  our  nature,  that, 
when  two  things  have  been  found  connected  in  time  past, 
the  appearance  of  the  one  produces  the  belief  of  the  other. 

I  think  the  ingenious  author  of  the  "  Treatise  of  Hu- 
man Nature  "  first  observed,  That  our  belief  of  the  con- 
tinuance of  the  laws  of  nature  cannot  be  founded  either 
upon  knowledge  or  probability:  but,  far  from  conceiving 
it  to  be  an  original  principle  of  the  mind,  he  endeavours 
to  account  for  it  from  his  favourite  hypothesis,  That  be- 
lief is  nothing  but  a  certain  degree  of  vivacity  in  the  idea 
of  the  thing  believed.  I  made  a  remark  upon  this  cu- 
rious hypothesis  in  the  second  chapter,  and  shall  now 
make  another. 

The  belief  which  we  have  in  perception,  is  a  belief  of 
the  present  existence  of  the  object;  that  which  we  have  in 
memory,  is  a  belief  of  its  past  existence;  the  belief  of 
which  we  are  now  speaking  is  a  belief  of  its  future  ex- 
istence; and  in  imagination  there  is  no  belief  at  all. 
Now,  I  would  gladly  know  of  this  author,  how  one 
degree  of  vivacity  fixes  the  existence  of  the  object 
to  the  present  moment;  another  carries  it  back  to 
time  past;  a  third,  taking  a  contrary  direction,  carries 
it  into  futurity;  and  a  fourth  carries  it  out  of  ex- 
istence altogether.  Suppose,  for  instance,  that  I  see 
the  sun  rising  out  of  the  sea;  I  remember  to  have 
seen  him  rise  yesterday;  I  believe  he  will  rise  to-mor- 
row near  the  same  place;  I  can  likewise  imagine  him  ris- 
ing in  that  place,  without  any  belief  at  all.  Now,  ac- 
cording to  this  sceptical  hypothesis,  this  perception,  this 
memory,  this  foreknowledge,  and  this  imagination,  are 
all  the  same  idea,  diversified  only  by  different  degrees  of 
vivacity.  The  perception  of  the  sun  rising  is  the  most 
lively  idea;  the  memory  of  his  rising  yesterday  is  the  same 
idea  a  little  more  faint;  the  belief  of  his  rising  to-morrow 


SEC.  XXIV.]  THE  PHILOSOPHY  OF  REID.  331 

is  the  same  idea  yet  fainter;  and  the  imagination  of  his 
rising  is  still  the  same  idea,  but  faintest  of  all.  One 
is  apt  to  think,  that  this  idea  might  gradually  pass 
through  all  possible  degrees  of  vivacity  without  stirring 
out  of  its  place.  But,  if  we  think  so,  we  deceive  our- 
selves: for  no  sooner  does  it  begin  to  grow  languid  than 
it  moves  backward  into  time  past.  Supposing  this  to  be 
granted,  we  expect,  at  least,  that,  as  it  moves  backward 
by  the  decay  of  its  vivacity,  the  more  that  vivacity  decays 
it  will  go  back  the  farther,  until  it  remove  quite  out  of 
sight.  But  here  we  are  deceived  again;  for  there  is  a 
certain  period  of  this  declining  vivacity  when,  as  if  it  had 
met  an  elastic  obstacle  in  its  motion  backward,  it  sud- 
denly rebounds  from  the  past  to  the  future,  without  tak- 
ing the  present  in  its  way.  And  now,  having  got  into  the 
regions  of  futurity,  we  are  apt  to  think  that  it  has  room 
enough  to  spend  all  its  remaining  vigour:  but  still  we 
are  deceived:  for,  by  another  sprightly  bound,  it  mounts 
up  into  the  airy  region  of  imagination.  So  that  ideas,  in 
the  gradual  declension  of  their  vivacity,  seem  to  imitate 
the  inflection  of  verbs  in  grammar.  They  begin  with 
the  present,,  and  proceed  in  order  to  the  preterite,  the 
future,  and  the  indefinite.  This  article  of  the  scep- 
tical creed  is  indeed  so  full  of  mystery,  on  whatever 
side  we  view  it,  that  they  who  hold  that  creed  are 
very  injuriously  charged  with  incredulity ;  for,  to  me, 
it  appears  to  require  as  much  faith  as  that  of  St.  Atha- 
nasius. 

However,  we  agree  with  the  author  of  the  ' '  Treatise 
of  Human  Nature,"  in  this,  That  our  belief  of  the  con- 
tinuance of  nature's  laws  is  not  derived  from  reason.  It 
is  an  instinctive  prescience  of  the  operations  of  na- 
ture very  like  to  that  prescience  of  human  actions 
which  makes  us  rely  upon  the  testimony  of  our  fel- 
low-creatures ;  and  as,  without  the  latter,  we  should  be 
incapable  of  receiving  information  from  men  by  lan- 
guage, so,  without  the  former,  we  should  be  incapable 


332  THE  PHILOSOPHY  OF  REID.  [Cu.  VI. 

of  receiving  the  information  of  nature  by  means  of  ex- 
perience. 

All  our  knowledge  of  nature  beyond  our  original 
perceptions,  is  got  by  experience,  and  consists  in 
the  interpretation  of  natural  signs.  The  constancy 
of  nature's  laws  connects  the  sign  with  the  thing  sig- 
nified; and,  by  the  natural  principle  just  now  ex- 
plained, we  rely  upon  the  continuance  of  the  connec- 
tions which  experience  hath  discovered;  and  thus  the  ap- 
pearance of  the  sign  is  followed  by  the  belief  of  the 
thing  signified. 

Upon  this  principle  of  our  constitution,  not  only 
acquired  perception,  but  all  inductive  reasoning,  and  all 
our  reasoning  from  analogy,  is  grounded;  and,  therefore, 
for  want  of  another  name,  we  shall  beg  leave  to  call  it 
the  inductive  principle.  It  is  from  the  force  of  this  princi- 
ple that  we  immediately  assent  to  that  axiom  upon  which 
all  our  knowledge  of  nature  is  built,  That  effects  of  the 
same  kind  must  have  the  same  cause;  for  effects  and 
causes,  in  the  operations  of  nature,  mean  nothing  but 
signs  and  the  things  signified  by  them.  We  perceive 
no  proper  causality  or  efficiency  in  any  natural  cause; 
but  only  a  connection  established  by  the  course  of 
nature  between  it  and  what  is  called  its  effect.  Antece- 
dently to  all  reasoning,  we  have,  by  our  constitution,  an 
anticipation  that  there  is  a  fixed  and  steady  course  of 
nature:  arid  we  have  an  eager  desire  to  discover  this 
course  of  nature.  We  attend  to  every  conjunction  of 
things  which  presents  itself,  and  expect  the  continuance 
of  that  conjunction.  And,  when  such  a  conjunction 
has  been  often  observed,  we  conceive  the  things  to  be 
naturally  connected,  and  the  appearance  of  one,  without 
any  reasoning  or  reflection,  carries  along  with  it  the  be- 
lief of  the  other. 

If  any  reader  should  imagine  that  the  inductive  prin- 
ciple may  be  resolved  into  what  philosophers  usually 
call  the  association  of  ideas,  let  him  observe,  that,  by  this 


SEC.  XXIV,]  THE  PHILOSOPHY  OF  REID.  333 

principle,  natural  signs  are  not  associated  with  the  idea 
only,  but  with  the  belief  of  the  things  signified.  Now, 
this  can  with  no  propriety  be  called  an  association  of 
ideas,  unless  ideas  and  belief  be  one  and  the  same  thing. 
A  child  has  found  the  prick  of  a  pin  conjoined  with 
pain ;  hence  he  believes,  and  knows,  that  these  things 
are  naturally  connected ;  he  knows  that  the  one  will 
always  follow  the  other.  If  any  man  will  call  this  only 
an  association  of  ideas,  I  dispute  not  about  words, 
but  I  think  he  speaks  very  improperly.  For,  if  we 
express  it  in  plain  English,  it  is  a  prescience  that  things 
which  he  hath  found  conjoined  in  time  past,  will  be 
conjoined  in  time  to  come.  And  this  prescience  is  not 
the  effect  of  reasoning,  but  of  an  original  principle 
of  human  nature,  which  I  have  called  the  inductive 
principle. 

This  principle,  like  that  of  credulity,  is  unlimited  in 
infancy,  and  gradually  restrained  and  regulated  as  we 
grow  up.  It  leads  us  often  into  mistakes;  but  is  of  in- 
finite advantage  upon  the  whole.  By  it,  the  child  once 
burnt  shuns  the  fire;  by  it,  he  likewise  runs  away  from 
the  surgeon  by  whom  he  was  inoculated.  It  is  better 
that  he  should  do  the  last,  than  that  he  should  not  do 
the  first. 

But  the  mistakes  we  are  led  into  by  these  two  natural 
principles,  are  of  a  different  kind.  Men  sometimes  lead 
us  into  mistakes,  when  we  perfectly  understand  their 
language,  by  speaking  lies.  But  Nature  never  misleads 
us  in  this  way:  her  language  is  always  true;  and  it  is 
only  by  misinterpreting  it  that  we  fall  into  error.  There 
must  be  many  accidental  conjunctions  of  things,  as  well 
as  natural  connections;  and  the  former  are  apt  to  be 
mistaken  for  the  latter.  Thus,  in  the  instance  above 
mentioned,  the  child  connected  the  pain  of  inoculation 
with  the  surgeon;  whereas  it  was  really  connected  with 
the  incision  only.  Philosophers,  and  men  of  science 
are  not  exempted  from  such  mistakes;  indeed,  all  false 


334  THE  PHILOSOPHY  OF  REID.  [Cn.  VI. 

reasoning  in  philosophy  is  owing  to  them;  it  is  drawn 
from  experience  and  analogy,  as  well  as  just  reasoning, 
otherwise  it  could  have  no  verisimilitude;  but  the  one  is 
an  unskilful  and  rash,  the  other  a  just  and  legitimate 
interpretation  of  natural  signs.  If  a  child,  or  a  man  of 
common  understanding,  were  put  to  interpret  a  book  of 
science,  written  in  his  mother  tongue,  how  many  blun- 
ders and  mistakes  would  he  be  apt  to  fall  into  ?  Yet 
he  knows  as  much  of  this  language  as  is  necessary  for 
his  manner  of  life. 

The  language  of  Nature  is  the  universal  study;  and 
the  students  are  of  different  classes.  Brutes,  idiots,  and 
children  employ  themselves  in  this  study,  and  owe  to  it 
all  their  acquired  perceptions.  Men  of  common  under- 
standing make  a  greater  progress,  and  learn,  by  a  small 
degree  of  reflection,  many  things  of  which  children  are 
ignorant. 

Philosophers  fill  up  the  highest  form  in  this  school, 
and  are  critics  in  the  language  of  nature.  All  these 
different  classes  have  one  teacher — Experience,  en- 
lightened by  the  inductive  principle.  Take  away  the 
light  of  this  inductive  principle,  and  Experience  is  as 
blind  as  a  mole:  she  may,  indeed,  feel  what  is  present, 
and  what  immediately  touches  her;  but  she  sees  nothing 
that  is  either  before  or  behind,  upon  the  right  hand  or 
upon  the  left,  future  or  past. 

The  rules  of  inductive  reasoning,  or  of  a  just  interpre- 
tation of  Nature,  as  well  as  the  fallacies  by  which  we  are 
apt  to  misinterpret  her  language,  have  been,  with 
wonderful  sagacity,  delineated  by  the  great  genius  of 
Lord  Bacon:  so  that  his  "Novum  Qrganum"  may  justly 
be  called  "A  Grammar  of  the  Language  of  Nature." 
It  adds  greatly  to  the  merit  of  this  work,  and  atones  for 
its  defects,  that,  at  the  time  it  was  written,  the  world  had 
not  seen  any  tolerable  model  of  inductive  reasoning, 
from  which  the  rules  of  it  might  be  copied.  The  arts  of 
poetry  and  eloquence  were  grown  up  to  perfection  when 


SBC.  XXIV.]  THE  PHILOSOPHY  OF  REID.  335 

Aristotle  described  them;  but  the  art  of  interpreting 
Nature  was  yet  in  embryo  when  Bacon  delineated  its 
manly  features  and  proportions.  Aristotle  drew  his 
rules  from  the  best  models  of  those  arts  that  have  yet 
appeared;  but  the  best  models  of  inductive  reasoning 
that  have  yet  appeared,  which  I  take  to  be  the  third 
book  of  the  "Principia,"  and  the  "Optics,"  of  Newton, 
were  drawn  from  Bacon's  rules.  The  purpose  of  all 
those  rules,  is  to  teach  us  to  distinguish  seeming,  or  ap- 
parent connections  of  things,  in  the  course  of  nature, 
from  such  as  are  real. 

They  that  are  unskilful  in  inductive  reasoning,  are 
more  apt  to  fall  into  error  in  their  reasonings  from  the 
phaenomena  of  nature  than  in  their  acquired  perceptions; 
because  we  often  reason  from  a  few  instances,  and  there- 
by are  apt  to  mistake  accidental  conjunctions  of  things 
for  natural  connections:  but  that  habit  of  passing,  with- 
out reasoning,  from  the  sign  to  the  thing  signified,  which 
constitutes  acquired  perception,  must  be  learned  by 
many  instances  or  experiments;  and  the  number  of  ex- 
periments serves  to  disjoin  those  things  which  have  been 
accidentally  conjoined,'  as  well  as  to  confirm  our  belief 
of  natural  connections. 

From  the  time  that  children  begin  to  use  their  hands, 
Nature  directs  them  to  handle  everything  over  and  over, 
to  look  at  it  while  they  handle  it,  and  to  put  it  in 
various  positions,  and  at  various  distances  from  the 
eye.  We  are  apt  to  excuse  this  as  a  childish  diversion, 
because  they  must  be  doing  something,  and  have  not 
reason  to  entertain  themselves  in  a  more  manly  way. 
But,  if  we  think  more  justly,  we  shall  find,  that  they  are 
engaged  in  the  most  serious  and  important  study;  and, 
if  they  had  all  the  reason  of  a  philosopher,  they  could 
not  be  more  properly  employed.  For  it  is  this  childish 
employment  that  enables  them  to  make  the  proper  use 
of  their  eyes.  They  are  thereby  every  day  acquiring 
habits  of  perception,  which  are  of  greater  importance 


336  THE  PHILOSOPHY  OF  REID.  [Cn.  VI. 

than  anything  we  can  teach  them.  The  original  per- 
ceptions which  Nature  gave  them  are  few,  and  insuffi- 
cient for  the  purposes  of  life;  and,  therefore,  she  made 
them  capable  of  acquiring  many  more  perceptions  by 
habit.  And,  to  complete  her  work,  she  hath  given  them 
an  unwearied  assiduity  in  applying  to  the  exercises  by 
which  those  perceptions  are  acquired. 

This  is  the  education  which  Nature  gives  to  her  chil- 
dren. And,  since  we  have  fallen  upon  this  subject,  we 
may  add,  that  another  part  of  Nature's  education  is, 
That,  by  the  course  of  things,  children  must  often  exert 
all  their  muscular  force,  and  employ  all  their  ingenuity, ' 
in  order  to  gratify  their  curiosity,  and  satisfy  their  little 
appetites.  What  they  desire  is  only  to  be  obtained  at 
the  expense  of  labour  and  patience,  and  many  disap- 
pointments. By  the  exercise  of  body  and  mind  neces- 
sary for  satisfying  their  desires,  they  acquire  agility, 
strength,  and  dexterity  in  their  motions,  as  well  as  health 
and  vigour  to  their  constitutions;  they  learn  patience 
and  perseverance;  they  learn  to  bear  pain  without  dejec- 
tion, and  disappointment  without  despondence.  The 
education  of  Nature  is  most  perfect  in  savages,  who  have 
no  other  tutor;  and  we  see  that,  in  the  quickness  of  all 
their  senses,  in  the  agility  of  their  motions,  in  the  hardi- 
ness of  their  constitutions,  and  in  the  strength  of  their 
minds  to  bear  hunger,  thirst,  pain,  and  disappointment, 
they  commonly  far  exceed  the  civilized.  A  most  ingen- 
ious writer,  on  this  account,  seems  to  prefer  the  savage 
life  to  that  of  society.  But  the  education  of  Nature 
could  never  of  itself  produce  a  Rousseau.  It  is  the  in- 
tention of  Nature  that  human  education  should  be  joined 
to  her  institution,  in  order  to  form  the  man.  And  she 
hath  fitted  us  for  human  education,  by  the  natural  prin- 
ciples of  imitation  and  credulity,  which  discover  them- 
selves almost  in  infancy,  as  well  as  by  others  which  are  of 
later  growth. 

When  the  education  which  we  receive  from  men,  does 


SBC.  XXIV.  THE  PHILOSOPHY  OF  REID.  337 

not  give  scope  to  the  education  of  Nature,  it  is  wrong 
directed  ;  it  tends  to  hurt  our  faculties  of  perception, 
and  to  enervate  both  the  body  and  mind.  Nature  hath 
her  way  of  rearing  men,  as  she  hath  of  curing  their  dis- 
eases. The  art  of  medicine  is  to  follow  Nature,  to  imi- 
tate and  to  assist  her  in  the  cure  of  diseases  ;  and  the  art 
of  education  is  to  follow  Nature,  to  assist  and  to  imi- 
tate her  in  her  way  of  rearing  men.  The  ancient  inhab- 
itants of  the  Baleares  followed  Nature  in  the  manner  of 
teaching  their  children  to  be  good  archers,  when  they 
hung  their  dinner  aloft  by  a  thread,  and  left  the  younkers 
to  bring  it  down  by  their  skill  in  archery. 

The  education  of  Nature,  without  any  more  human 
care  than  is  necessary  to  preserve  life,  makes  a  perfect 
savage.  Human  education,  joined  to  that  of  Nature, 
may  make  a  good  citizen,  a  skilful  artisan,  or  a  well- 
bred  man  ;  but  reason  and  reflection  must  superadd 
their  tutory,  in  order  to  produce  a  Rousseau,  a  Bacon,  or 
a  Newton. 

Notwithstanding  the  innumerable  errors  committed 
in  human  education,  there  is  hardly  any  education  so 
bad  as  to  be  worse  than  none.  And  I  apprehend  that, 
if  even  Rousseau  were  to  choose  whether  to  educate  a 
son  among  the  French,  the  Italians,  the  Chinese,  or 
among  the  Eskimaux,  he  would  not  give  the  preference 
to  the  last. 

When  Reason  is  properly  employed,  she  will  confirm 
the  documents  of  Nature,  which  are  always  true  and 
wholesome ;  she  will  distinguish,  in  the  documents  of 
human  education,  the  good  from  the  bad,  rejecting  the 
last  with  modesty,  and  adhering  to  the  first  with  rever- 
ence. 

Most  men  continue  all  their  days  to  be  just  what 
Nature  and  human  education  made  them.  Their  man- 
ners, their  opinions,  their  virtues,  and  their  vices,  are 
all  got  by  habit,  imitation,  and  instruction  ;  and  reason 
has  little  or  no  share  in  forming  them. 


338  THE  PHILOSOPHY  OF  REID,  [Cn.  VII. 


CHAPTER    VII. 
CONCLUSION. 

CONTAINING    REFLECTIONS    UPON  THE  OPINIONS    OF    PHILOSO- 
PHERS ON  THIS  SUBJECT. 

THERE  are  two  ways  in  which  men  may  form  their 
notions  and  opinions  concerning  the  mind,  and  con- 
cerning its  powers  and  operations.  The  first  is  the  only 
way  that  leads  to  truth ;  but  it  is  narrow  and  rugged, 
and  few  have  entered  upon  it.  The  second  is  broad 
and  smooth,  and  hath  been  much  beaten,  not  only  by 
the  vulgar,  but  even  by  philosophers  ;  it  is  sufficient  for 
common  life,  and  is  well  adapted  to  the  purposes  of 
the  poet  and  orator  :  but,  in  philosophical  disquisitions 
concerning  the  mind,  it  leads  to  error  and  delusion. 

We  may  call  the  first  of  these  ways,  the  way  of  reflec- 
tion. When  the  operations  of  the  mind  are  exerted,  we 
are  conscious  of  them  ;  and  it  is  in  our  power  to  attend 
to  them  ;  and  to  reflect  upon  them,  until  they  become 
familiar  objects  of  thought.  This  is  the  only  way  in 
which  we  can  form  just  and  accurate  notions  of  those 
operations.  But  this  attention  and  reflection  is  so  diffi- 
cult to  man,  surrounded  on  all  hands  by  external  ob- 
jects which  constantly  solicit  his  attention,  that  it  has 
been  very  little  practised,  even  by  philosophers.  In 
the  course  of  this  inquiry,  we  have  had  many  occasions 
to  shew  how  little  attention  hath  been  given  to  the  most 
familiar  operations  of  the  senses. 

The  second,  and  the  most  common  way,  in  which 
men  form  their  opinions  concerning  the  mind  and  its 


CH.  VII.]  THE  PHILOSOPHY  OF  REID.  339 

operations,  we  may  call  the  way  of  analogy.  There  is 
nothing  in  the  course  of  nature  so  singular,  but  we  can 
find  some  resemblance,  or  at  least  some  analogy,  be- 
tween it  and  other  things  with  which  we  are  acquainted. 
The  mind  naturally  delights  in  hunting  after  such  analo- 
gies, and  attends  to  them  with  pleasure.  From  them, 
poetry  and  wit  derive  a  great  part  of  their  charms  ;  and 
eloquence,  not  a  little  of  its  persuasive  force. 

Besides  the  pleasure  we  receive  from  analogies,  they 
are  of  very  considerable  use,  both  to  facilitate  the  con- 
ception of  things,  when  they  are  not  easily  apprehended 
without  such  a  handle,  and  to  lead  us  to  probable  con- 
jectures about  their  nature  and  qualities,  when  we  want 
the  means  of  more  direct  and  immediate  knowledge. 
When  I  consider  that  the  planet  Jupiter,  in  like  manner 
as  the  earth,  rolls  round  his  own  axis,  and  revolves 
round  the  sun,  and  that  he  is  enlightened  by  several  sec- 
ondary planets,  as  the  earth  is  enlightened  by  the  moon, 
I  am  apt  to  conjecture,  from  analogy,  that,  as  the  earth 
by  these  means  is  fitted  to  be  the  habitation  of  various 
orders  of  animals,  so  the  olanet  Jupiter  is,  by  the  like 
means,  fitted  for  the  same  purpose ;  and,  having  no 
argument  more  direct  and  conclusive  to  determine  me 
in  this  point,  I  yield,  to  this  analogical  reasoning,  a  de- 
gree of  assent  proportioned  to  its  strength.  When  I 
observe  that  the  potato  plant  very  much  resembles  the 
solatium  in  its  flower  and  fructification,  and  am  informed 
that  the  last  is  poisonous,  I  am  apt  from  analogy  to  have 
some  suspicion  of  the  former  :  but,  in  this  case,  I  have 
access  to  more  direct  and  certain  evidence ;  and,  there- 
fore, ought  not  to  trust  to  analogy,  which  would  lead 
me  into  an  error. 

Arguments  from  analogy  are  always  at  hand,  and 
grow  up  spontaneously  in  a  fruitful  imagination  ;  while 
arguments  that  are  more  direct  and  more  conclusive 
often  require  painful  attention  and  application  ;  and 
therefore  mankind  in  general  have  been  very  much  dis- 


340  THE  PHILOSOPHY   OF  REID.  [Cn.  VII. 

posed  to  trust  to  the  former.  If  one  attentively  exam- 
ines the  systems  of  the  ancient  philosophers,  either  con- 
cerning the  material  world,  or  concerning  the  mind,  he 
will  find  them  to  be  built  solely  upon  the  foundation  of 
analogy.  Lord  Bacon  first  delineated  the  strict  and  se- 
vere method  of  induction  ;  since  his  time,  it  has  been 
applied  with  very  happy  success  in  some  parts  of  natural 
philosophy: — and  hardly  in  anything  else.  But  there  is 
no  subject  in  which  mankind  are  so  much  disposed  to 
trust  to  the  analogical  way  of  thinking  and  reasoning,  as 
in  what  concerns  the  mind  and  its  operations  ;  because, 
to  form  clear  and  distinct  notions  of  those  operations  in 
the  direct  and  proper  way,  and  to  reason  about  them, 
requires  a  habit  of  attentive  reflection,  of  which  few  are 
capable,  and  which,  even  by  those  few,  cannot  be  at- 
tained without  much  pains  and  labour. 

Every  man  is  apt  to  form  his  notions  of  things  diffi- 
cult to  be  apprehended,  or  less  familiar,  from  their  an- 
alogy to  things  which  are  more  familiar.  Thus,  if  a  man 
bred  to  the  seafaring  life,  and  accustomed  to  think  and 
talk  only  of  matters  relating  to  navigation,  enters  into 
discourse  upon  any  other  subject,  it  is  well  known  that 
the  language  and  the  notions  proper  to  his  own  profes- 
sion are  infused  into  every  subject,  and  all  things  are 
measured  by  the  rules  of  navigation  ;  and,  if  he  should 
take  it  into  his  head  to  philosophize  concerning  the  fac- 
ulties of  the  mind,  it  cannot  be  doubted  but  he  would 
draw  his  notions  from  the  fabric  of  his  ship,  and  would 
find  in  the  mind,  sails,  masts,  rudder,  and  compass.* 

Sensible  objects,  of  one  kind  or  other;  do  no  less  oc- 
cupy and  engross  the  rest  of  mankind,  than  things  re- 
lating to  navigation  the  seafaring  man.  For  a  consid- 
erable part  of  life,  we  can  think  of  nothing  but  the 
objects  of  sense  ;  and,  to  attend  to  objects  of  another  na- 


*  See  "Essays  on  the  Intellectual  Powers,"  Ess.  VI.,  ch.  viii., 
Nos.  2  and  6.— H, 


CH.  VII.]  THE   PHILOSOPHY   OF  REID.  341 

ture,  so  as  to  form  clear  and  distinct  notions  of  them,  is 
no  easy  matter,  even  after  we  come  to  years  of  reflection. 
The  condition  of  mankind,  therefore,  affords  good  reason 
to  apprehend  that  their  language,  and  their  common 
notions  concerning  the  mind  and  its  operations,  will 
be  analogical,  and  derived  from  the  objects  of  sense  ; 
and  that  these  analogies  will  be  apt  to  impose  upon 
philosophers,  as  well  as  upon  the  vulgar,  and  to  lead 
them  to  materialize  the  mind  and  its  faculties  :  and 
experience  abundantly  confirms  the  truth  of  this. 

How  generally  men  of  all  nations,  and  in  all  ages  of 
the  world,  have  conceived  the  soul,  or  thinking  princi- 
ple in  man,  to  be  some  subtile  matter,  like  breath  or 
wind,  the  names  given  to  it  almost  in  all  languages  suffi- 
ciently testify.  We  have  words  which  are  proper,  and 
not  analogical,  to  express  the  various  ways  in  which  we 
perceive  external  objects  by  the  senses — such  as  feeling, 
sight,  taste;  but  we  are  often  obliged  to  use  these  words 
analogically,  to  express  other  powers  of  the  mind  which 
are  of  a  very  different  nature.  And  the  powers  which 
imply  some  degree  of  reflection,  have  generally  no 
names  but  such  as  are  analogical.  The  objects  of 
thought  are  said  to  be  in  the  mind— to  be  apprehended, 
comprehended,  conceived,  imagined,  retained,  weighed,  ru- 
minated. 

It  does  not  appear  that  the  notions  of  the  ancient 
philosophers,  with  regard  to  the  nature  of  the  soul,  were 
much  more  refined  than  those  of  the  vulgar,  or  that  they 
were  formed  in  any  other  way.  We  shall  distinguish  the 
philosophy  that  regards  our  subject  into  the  old  and  the 
new.  The  old  reached  down  to  Des  Cartes,  who  gave 
it  a  fatal  blow,  of  which  it  has  been  gradually  expiring 
ever  since,  and  is  now  almost  extinct.  Des  Cartes  is  the 
father  of  the  new  philosophy  that  relates  to  this  subject ; 
but  it  hath  been  gradually  improving  since  his  time, 
upon  the  principles  laid  down  by  him.  The  old  philoso- 
phy seems  to  have  been  purely  analogical  ;  the  new  is 


342  THE  PHILOSOPHY   OF  REID.  [Cur.  VII. 

more  derived  from  reflection,  but  still  with  a  very  con- 
siderable mixture  of  the  old  analogical  notions. 

Because  the  objects  of  sense  consist  of  matter  and 
form,  the  ancient  philosophers  conceived  everything  to 
belong  to  one  of  these,  or  to  be  made  up  of  both. 
Some,  therefore,  thought  that  the  soul  is  a  particular 
kind  of  subtile  matter,  separable  from  our  gross  bodies  ; 
others  thought  that  it  is  only  a  particular  form  of  the 
body,  and  inseparable  from  it.  For  there  seem  to  have 
been  some  among  the  ancients,  as  well  as  among  the 
moderns,  who  conceived  that  a  certain  structure  or 
organization  of  the  body,  is  all  that  is  necessary  to  ren- 
der it  sensible  and  intelligent.  The  different  powers  of 
the  mind  were,  accordingly,  by  the  last  sect  of  philoso- 
phers, conceived  to  belong  to  different  parts  of  the  body 
— as  the  heart,  the  brain,  the  liver,  the  stomach,  the 
blood. 

They  who  thought  that  the  soul  is  a  subtile  matter, 
separable  from  the  body,  disputed  to  which  of  the  four 
elements  it  belongs — whether  to  earth,  water,  air,  or  fire. 
Of  the  three  last,  each  had  its  particular  advocates.  But 
some  were  of  opinion,  that  it  partakes  of  all  the  elements: 
that  it  must  have  something  in  its  composition  similar 
to  everything  we  perceive;  and  that  we  perceive  earth  by 
the  earthly  part;  water,  by  the  watery  part;  and  fire,  by 
the  fiery  part  of  the  soul.  Some  philosophers,  not 
satisfied  with  determining  of  what  kind  of  matter  the  soul 
is  made,  inquired  likewise  into  its  figure,  which  they 
determined  to  be  spherical,  that  it  might  be  the  more  fit 
for  motion.  The  most  spiritual  and  sublime  notion  con- 
cerning the  nature  of  the  soul,  to  be  met  with  among  the 
ancient  philosophers,  I  conceive  to  be  that  of  the 
Platonists,  who  held  that  it  is  made  of  that  celestial  and 
incorruptible  matter  of  which  the  fixed  stars  were  made, 
and,  therefore,  has  a  natural  tendency  to  rejoin  its  proper 
element.  I  am  at  a  loss  to  say,  in  which  of  these  classes 
of  philosophers  Aristotle  ought  to  be  placed.  He  defines 


CH.  VII.]  THE  PHILOSOPHY   OF   REID.  343 

the  soul  to  be,  The  first  ivr^e^EioLof  a  natural  body  which 
has  potential  life.  I  beg  to  be  excused  from  translating 
the  Greek  word,  because  I  know  not  the  meaning 
of  it. 

The  notions  of  the  ancient  philosophers  with  regard  to 
the  operations  of  the  mind,  particularly  with  regard  to 
perception  and  ideas,  seem  likewise  to  have  been  formed 
by  the  same  kind  of  analogy. 

Plato,  of  the  writers  that  are  extant,  first  introduced  the 
word  idea  into  philosophy;  but  his  doctrine  upon  this 
subject  had  somewhat  peculiar.  He  agreed  with  the  rest 
of  the  ancient  philosophers  in  this — that  all  things  con- 
sist of  matter  and  form;  and  that  the  matter  of  which  all 
things  were  made,  existed  from  eternity,  without  form: 
but  he  likewise  believed  that  there  are  eternal  forms  of  all 
possible  things  which  exist,  without  matter;  and  to  these 
eternal  and  immaterial  forms  he  gave  the  name  of  ideas; 
maintaining  that  they  are  the  only  object  of  true  knowl- 
edge. It  is  of  no  great  moment  to  us,  whether  he  bor- 
rowed these  notions  from  Parmenides,  or  whether  they 
were  the  issue  of  his  own  creative  imagination.  The 
latter  Platonists  seem  to  have  improved  upon  them,  in 
conceiving  those  ideas,  or  eternal  forms  of  things,  to  exist 
not  of  themselves,  but  in  the  divine  mind,  and  to  be  the 
models  and  patterns  according  to  which  all  things  were 
made: — 

"  Then  liv'd  the  Eternal  One;  then,  deep  retir'd 
In  his  unfathom'd  essence,  view'd  at  large 
The  uncreated  images  of  things." 

To  these  Platonic  notions,  that  of  Malebranche  is  very 
nearly  allied.  This  author  seems,  more  than  any  other, 
to  have  been  aware  of  the  difficulties  attending  the  com- 
mon hypothesis  concerning  ideas — to  wit,  That  ideas 
of  all  objects  of  thought  are  in  the  human  mind;  and, 
therefore,  in  order  to  avoid  those  difficulties,  makes  the 
ideas  which  are  the  immediate  objects  of  human  thought, 


344  THE  PHILOSOPHY  OF  REID.  [CH,  VII. 

to  be  the  ideas  of  things  in  the  Divine  mind,  who,  being 
intimately  present  to  every  human  mind,  may  discover 
his  ideas  to  it,  as  far  as  pleaseth  him. 

The  Platonists  and  Malebranche  excepted,  all  other 
philosophers,  as  far  as  I  know,  have  conceived  that  there 
are  ideas  or  images  of  every  object  of  thought  in  the 
human  mind,  or,  at  least,  in  some  part  of  the  brain, 
where  the  mind  is  supposed  to  have  its  residence. 

Aristotle  had  no  good  affection  to  the  word  idea,  and 
seldom  or  never  uses  it  but  in  refuting  Plato's  notions 
about  ideas.  He  thought  that  matter  may  exist  without 
form;  but  that  forms  cannot  exist  without  matter.  But, 
at  the  same  time,  he  taught,  That  there  can  be  no 
sensation,  no  imagination,  nor  intellection,  without 
forms,  phantasms,  or  species  in  the  mind;  and  that  things 
sensible  are  perceived  by  sensible  species,  and  things 
intelligible  by  intelligible  species.  His  followers  taught, 
more  explicitly,  that  those  sensible  and  intelligible  species 
are  sent  forth  by  the  objects,  and  make  their  impressions 
upon  the  passive  intellect;  and  that  the  active  intellect 
perceives  them  in  the  passive  intellect.  And  this  seems 
to  have  been  the  common  opinion  while  the  Peripatetic 
philosophy  retained  its  authority. 

The  Epicurean  doctrine,  as  explained  by  Lucretius, 
though  widely  different  from  the  Peripatetic  in  many 
things,  is  almost  the  same  in  this.  He  affirms,  that 
slender  films  or  ghosts  (tenuia  rerum  simulacra)  are  still 
going  off  from  all  things,  and  flying  about;  and  that  these, 
being  extremely  subtile,  easily  penetrate  our  gross  bodies, 
and,  striking  upon  the  mind,  cause  thought  and  imag- 
ination. 

After  the  Peripatetic  system  had  reigned  above  a 
thousand  years  in  the  schools  of  Europe,  almost  without 
a  rival,  it  sunk  before  that  of  Des  Cartes;  the  perspicuity 
of  whose  writings  and  notions,  contrasted  with  the 
obscurity  of  Aristotle  and  his  commentators,  created  a 
strong  prejudice  in  favor  of  this  new  philosophy.  The 


CH.VH.]  THE  PHILOSOPHY  OF  REID.  345 

characteristic  of  Plato's  genius  was  sublimity,  that  of 
Aristotle's,  subtilty;  but  Des  Cartes  far  excelled  both  in 
perspicuity,  and  bequeathed  this  spirit  to  his  successors. 
The  system  which  is  now  generally  received,  with  regard 
to  the  mind  and  its  operations,  derives  not  only  its  spirit 
from  Des  Cartes,  but  its  fundamental  principles;  and, 
after  all  the  improvements  made  by  Malebranche,  Locke, 
Berkeley,  and  Hume,  may  still  be  called  the  Cartesian 
system:  we  shall,  therefore,  make  some  remarks  upon  its 
spirit  and  tendency  in  general,  and  upon  its  doctrine  con- 
cerning ideas  in  particular. 

i.  It  may  be  observed,  That  the  method  which  Des 
Cartes  pursued,  naturally  led  him  to  attend  more  to  the 
operations  of  the  mind  by  accurate  reflection,  and  to 
trust  less  to  analogical  reasoning  upon  this  subject,  than 
any  philosopher  had  done  before  him.  Intending  to 
build  a  system  upon  a  new  foundation,  he  began  with  a 
resolution  to  admit  nothing  but  what  was  absolutely 
certain  and  evident.  He  supposed  that  his  senses,  his 
memory,  his  reason,  and  every  other  faculty  to  which  we 
trust  in  common  life,  might  be  fallacious;  and  resolved 
to  disbelieve  everything,  until  he  was  compelled  by 
irresistible  evidence  to  yield  assent. 

In  this  method  of  proceeding,  what  appeared  to  him, 
first  of  all,  certain  and  evident,  was,  That  he  thought — 
that  he  doubted — that  he  deliberated.  In  a  word,  the 
operations  of  his  own  mind,  of  which  he  was  conscious, 
must  be  real,  and  no  delusion;  and,  though  all  his 
other  faculties  should  deceive  him,  his  consciousness 
could  not.*  This,  therefore,  he  looked  upon  as  the  first 
of  all  truths.  This  was  the  first  firm  ground  upon  which 
he  set  his  foot,  after  being  tossed  in  the  ocean  of  scepti- 
cism ;  and  he  resolved  to  build  all  knowledge  upon  it, 
without  seeking  after  any  more  first  principles. 

*  Des  Cartes  did  not  commit  Reid's  error  of  making  conscious- 
ness a  co-ordinate  and  special  faculty.— H. 


346  THE  PHILOSOPHY  OF  REID.  [Cn.Vll. 

As  every  other  truth,  therefore,  and  particularly  the 
existence  of  the  objects  of  sense,  was  to  be  deduced  by  a 
train  of  strict  argumentation  from  what  he  knew  by  con- 
sciousness, he  was  naturally  led  to  give  attention  to  the 
operations  of  which  he  was  conscious,  without  borrowing 
his  notions  of  them  from  external  things. 

It  was  not  in  the  way  of  analogy,  but  of  attentive  re- 
flection, that  he  was  led  to  observe,  That  thought,  voli- 
tion, remembrance,  and  the  other  attributes  of  the  mind, 
are  altogether  unlike  to  extension,  to  figure,  and  to  all 
the  attributes  of  body;  that  we  have  no  reason,  therefore, 
to  conceive  thinking  substances  to  have  any  resemblance 
to  extended  substances;  and  that,  as  the  attributes  of  the 
thinking  substance  are  things  of  which  we  are  conscious, 
we  may  have  a  more  certain  and  immediate  knowledge 
of  them  by  reflection,  than  we  can  have  of  external  ob- 
jects by  our  senses. 

These  observations,  as  far  as  I  know,  were  first  made 
by  Des  Cartes;  and  they  are  of  more  importance,  and 
throw  more  light  upon  the  subject,  than  all  that  had  been 
said  upon  it  before.  They  ought  to  make  us  diffident 
and  jealous  of  every  notion  concerning  the  mind  and  its 
operations,  which  is  drawn  from  sensible  objects  in  the 
way  of  analogy,  and  to  make  us  rely  only  upon  accu- 
rate reflection,  as  the  source  of  all  real  knowledge  upon 
this  subject. 

2.  I  observe  that,  as  the  Peripatetic  system  has  a  ten- 
dency to  materialize  the  mind  and  its  operations,  so  the 
Cartesian  has  a  tendency  to  spiritualize  body  and  its 
qualities.  One  error,  common  to  both  systems,  leads 
to  the  first  of  these  extremes  in  the  way  of  analogy,  and 
to  the  last  in  the  way  of  reflection.  The  error  I  mean 
is,  That  we  can  know  nothing  about  body,  or  its  quali- 
ties, but  as  far  as  we  have  sensations  which  resemble 
those  qualities.  Both  systems  agreed  in  this:  but 
according  to  their  differing  methods  of  reasoning,  they 
drew  very  different  conclusions  from  it ;  the  Peripatetic 


CH.  VI1.1  THE  PHILOSOPHY  OP  REID.  347 

drawing  his  notions  of  sensation  from  the  qualities  of 
body;  the  Cartesian,  on  the  contrary,  drawing  his  no- 
tions of  the  qualities  of  body  from  his  sensations. 

The  Peripatetic,  taking  it  for  granted  that  bodies  and 
their  qualities  do  really  exist,  and  are  such  as  we  com- 
monly take  them  to  be,  inferred  from  them  the  nature  of 
his  sensations,  and  reasoned  in  this  manner: — Our  sensa- 
tions are  the  impressions  which  sensible  objects  make 
upon  the  mind,  and  may  be  compared  to  the  impression 
of  a  seal  upon  wax:  the  impression  is  the  image  or  form 
of  the  seal,  without  the  matter  of  it;  in  like  manner, 
every  sensation  is  the  image  or  form  of  some  sensible 
quality  of  the  object.  This  is  the  reasoning  of  Aristotle: 
and  it  has  an  evident  tendency  to  materialize  the  mind 
and  its  sensations. 

The  Cartesian,  on  the  contrary,  thinks  that  the  exist- 
ence of  body,  or  of  any  of  its  qualities,  is  not  to  be 
taken  as  a  first  principle ;  and  that  we  ought  to  admit 
nothing  concerning  it,  but  what,  by  just  reasoning,  can 
be  deduced  from  our  sensations;  and  he  knows  that,  by 
reflection,  we  can  form  clear  and  distinct  notions  of  our 
sensations,  without  borrowing  our  notions  of  them  by 
analogy  from  the  objects  of  sense.  The  Cartesians, 
therefore,  beginning  to  give  attention  to  their  sensations, 
first  discovered  that  the  sensations  corresponding  to 
secondary  qualities,  cannot  resemble  any  quality  of  body. 
Hence,  Des  Cartes  and  Locke  inferred,  that  sound,  taste, 
smell,  colour,  heat,  and  cold,  which  the  vulgar  took  to 
be  qualities  of  body,  were  not  qualities  of  body,  but 
mere  sensations  of  the  mind.*  Afterwards,  the  ingen- 

*  Des  Cartes  and  Locke  made  no  such  inference.  They  only 
maintained  (as  Reid  himself  states)  that  sound,  taste,  &c.,  as  sensa- 
tions in  us,  have  no  resemblance  to  any  quality  in  bodies.  If  the 
names,  therefore,  of  sound,  taste,  &c.,  were  to  be  employed  univo- 
cally — i.  <?.,  to  denote  always  things  the  same  or  similar — in  that 
case  they  argued  that  these  terms,  if  properly  significant  of  the  sen- 
sations, could  not  be  properly  applied  to  the  relative  qualities  in  ex- 


34$  THE  PHILOSOPHY  OF  REID.  [Cn.  VII. 

ious  Berkeley,  considering  more  attentively  the  nature  of 
sensation  in  general,  discovered  and  demonstrated,  that 
no  sensation  whatever  could  possibly  resemble  any  qual- 
ity of  an  insentient  being,  such  as  body  is  supposed  to 
be;  and  hence  he  inferred,  very  justly,  that  there  is  the 
same  reason  to  hold  extension,  figure,  and  all  the  pri- 
mary qualities,  to  be  mere  sensations,  as  there  is  to  hold 
the  secondary  qualities  to  be  mere  sensations.  Thus, 
by  just  reasoning  upon  the  Cartesian  principles,  matter 
was  stripped  of  all  its  qualities;  the  new  system,  by  a 
kind  of  metaphysical  sublimation,  converted  all  the  qual- 
ities of  matter  into  sensations,  and  spiritualized  body, 
as  the  old  had  materialized  spirit. 

The  way  to  avoid  both  these  extremes,  is  to  admit 
the  existence  of  what  we  see  and  feel  as  a  first  principle, 
as  well  as  the  existence  of  things  whereof  we  are  con- 
scious; and  to  take  our  notions  of  the  qualities  of  body, 
from  the  testimony  of  our  senses,  with  the  Peripatetics ; 
and  our  notions  of  our  sensations  from  the  testimony 
of  consciousness,  with  the  Cartesians. 

ternal  things.  This  is  distinctly  stated  both  by  Des  Cartes  and 
Locke.  But  Des  Cartes  and  the  Cartesians  observe  that  the  terms 
in  question  are  equivocally  used;  being  commonly  applied  both  to 
that  in  things  which  occasions  the  sensation  in  us,  and  to  that  sen- 
sation itself.  Nay,  the  Cartesians,  to  avoid  the  ambiguity,  distin- 
guished the  two  relatives  by  different  names.  To  take  colour,  tor 
example:  they  called  colour,  as  a  sensation  in  the  mind,  formal 
colour;  colour,  as  a  quality  in  bodies  capable  of  producing  the  sensa- 
tion, primitive  or  radical  colour.  They  had  likewise  another  dis- 
tinction of  less  importance — that  of  secondary  or  derivative  colour; 
meaning  thereby  that  which  the  coloured  bodies  impress  upon  the 
external  medium.  Thus,  again,  primitive  or  radical  sound  was  the 
property  of  a  body  to  determine  a  certain  agitation  in  the  air  or 
other  medium;  secondary  or  derivative  sound,  that  agitation  in  the 
medium  itself  ;  formal  sound,  the  sensation  occasioned  by  the  im- 
pression made  by  the  radical  sound  mediately,  and  by  the  deriva- 
tive immediately,  upon  the  organ  of  hearing.  There  is  thus  no 
difference  between  Reid  and  the  Cartesians,  except  that  the  doctrine 
which  he  censures  is  in  fact  more  precise  and  explicit  than  his 
own, — H. 


CH.  VII.]  THE  PHILOSOPHY  OF  REID.  349 

3.  I  observe,  That'  the  modern  scepticism  is  the 
natural  issue  of  the  new  system;  and  that,  although  it 
did  not  being  forth  this  monster  until  the  year  1739,*  ^ 
may  be  said  to  have  carried  it  in  its  womb  from  the  be- 
ginning. 

The  old  system  admitted  all  the  principles  of  common 
sense  as  first  principles,  without  requiring  any  proof  of 
them;  and,  therefore,  though  its  reasoning  was  common- 
ly vague,  analogical,  and  dark,  yet  it  was  built  upon  a 
broad  foundation,  and  had  no  tendency  to  scepticism. 
We  do  not  find  that  any  Peripatetic  thought  it  incum- 
bent upon  him  to  prove  the  existence  of  a  material 
world;  but  every  writer  upon  the  Cartesian  system  at- 
tempted this,  until  Berkeley  clearly  demonstrated  the 
futility  of  their  arguments;  and  thence  concluded  that 
there  was  no  such  thing  as  a  material  world;  and  that 
the  belief  of  it  ought  to  be  rejected  as  a  vulgar  error. 

The  new  system  admits  only  one  of  the  principles  of 
common  sense  as  a  first  principle;  and  pretends,  by 
strict  argumentation,  to  deduce  all  the  rest  from  it. 
That  our  thoughts,  our  sensations,  and  every  thing  of 
which  we  are  conscious,  hath  a  real  existence,  is  admitted 
in  this  system  as  a  first  principle;  but  everything  else 
must  be  made  evident  by  the  light  of  reason.  Reason 
must  rear  the  whole  fabric  of  knowledge  upon  this  sin- 
gle principle  of  consciousness. 

There  is  a  disposition  in  human  nature  to  reduce 
things  to  as  few  principles  as  possible;f  and  this,  with- 
out doubt,  adds  to  the  beauty  of  a  system,  if  the  princi- 
ples are  able  to  support  what  rests  upon  them.  The 
mathematicians  glory,  very  justly,  in  having  raised  so 
noble  and  magnificent  a  system  of  science,  upon  the 
foundation  of  a  few  axioms  and  definitions.  This  love 

*  When  Hume's  "Treatise  of  Human  Nature  "  appeared.— H. 
f  See  "  Essays  on  the  Intellectual  Powers,"  p.  656,  sqq.  4to  edi- 
tion.—H. 


350  THE  PHILOSOPHY  OF  REID.  [CM.  VII. 

of  simplicity,  and  of  reducing  things  to  few  principles, 
hath  produced  many  a  false  system;  but  there  never  was 
any  system  in  which  it  appears  so  remarkably  as  that  of 
Des  Cartes.*  His  whole  system  concerning  matter  and 
spirit  is  built  upon  one  axiom,  expressed  in  one  word, 
cogito.  Upon  the  foundation  of  conscious  thought,  with 
ideas  for  his  materials,  he  builds  his  system  of  the  hu- 
man understanding,  and  attempts  to  account  for  all 
its  phenomena;  and  having,  as  he  imagined,  from  his 
consciousness,  proved  the  existence  of  matter;  upon  the 
existence  of  matter,  and  of  a  certain  quantity  of  motion 
originally  impressed  upon  it,  he  builds  his  system  of  the 
material  world,  and  attempts  to  account  for  all  its  phae- 
nomena. 

These  principles,  with  regard  to  the  material  system, 
have  been  found  insufficient;  and  it  has  been  made  evi- 
dent that,  besides  matter  and  motion,  we  must  admit 
gravitation,  cohesion,  corpuscular  attraction,  magnetism, 
and  other  centripetal  and  centrifugal  forces,  by  which 
the  particles  of  matter  attract  and  repel  each  other. 
Newton,  having  discovered  this,  and  demonstrated  that 
these  principles  cannot  be  resolved  into  matter  and  mo- 
tion, was  led,  by  analogy  and  the  love  of  simplicity,  to 
conjecture,  but  with  a  modesty  and  caution  peculiar  to 
him,  that  all  the  phenomena  of  the  material  world  de- 
pended upon  attracting  and  repelling  forces  in  the  parti- 
cles of  matter.  But  we  may  now  venture  to  say,  that 
this  conjecture  fell  short  of  the  mark.  For,  even  in  the 
unorganized  kingdom,  the  powers  by  which  salts,  crys- 
tals, spars,  and  many  other  bodies,  concrete  into  regular 
forms,  can  never  be  accounted  for  by  attracting  and  re- 
pelling forces  in  the  particles  of  matter.  And  in  the 
vegetable  and  animal  kingdoms,  there  are  strong  indica- 


*  We  must  except,  however,  before  Reid,  among  others,  the  sys- 
tem of  Spinoza,  and,  since  Reid,  those  of  Fichte,  Schelling,  Hegel, 
&c.— H. 


CH.  VII.]  THE  PHILOSOPHY  OF  REID.  3$  I 

tions  of  powers  of  a  different  nature  from  all  the  powers 
of  unorganized  bodies.  We  see,  then,  that,  although, 
in  the  structure  of  the  material  world,  there  is,  without 
doubt,  all  the  beautiful  simplicity  consistent  with  the 
purposes  for  which  it  was  made,  it  is  not  so  simple  as 
the  great  Des  Cartes  determined  it  to  be;  nay,  it  is  not  so 
simple  as  the  greater  Newton  modestly  conjectured  it  to 
be.  Both  were  misled  by  analogy,  and  the  love  of  sim- 
plicity. One  had  been  much  conversant  about  exten- 
sion, figure,  and  motion;  the  other  had  enlarged  his 
views  to  attracting  and  repelling  forces;  and  both  formed 
their  notions  of  the  unknown  parts  of  nature,  from  those 
with  which  they  were  acquainted,  as  the  shepherd  Tity- 
rus  formed  his  notion  of  the  city  of  Rome  from  his  coun- 
try village: — 

"  Urbem  quam  dicunt  Romam,  Meliboee,  putavi 
Stultus  ego,  huic  nostrae  similem,  quo  ssepe  solemus 
Pastores  ovium  teneros  depellere  foetus. 
Sic  canibus  catulos  similes,  sic  matribus  hoedos 
Noram:  sic  parvis  componere  magna  solebam." 

This  is  a  just  picture  of  the  analogical  way  of  thinking. 
But  to  come  to  the  system  of  Des  Cartes,  concerning 
the  human  understanding.  It  was  built,  as  we  have  ob- 
served, upon  consciousness  as  its  sole  foundation,  and 
with  ideas*  as  its  materials;  and  all  his  followers  have 
built  upon  the  same  foundation  and  with  the  same  ma- 
terials. They  acknowledge  that  Nature  hath  given  us 
various  simple  ideas.  These  are  analogous  to  the  mat- 
ter, of  Des  Cartes's  physical  system.  They  acknowledge, 
likewise,  a  natural  power,  by  which  ideas  are  com- 
pounded, disjoined,  associated,  compared.  This  is  an- 

*  There  is  no  valid  ground  for  supposing  that  Des  Cartes  meant 
by  ideas  aught  but  modifications  of  the  mind  itself.  That  the  ma- 
jority of  the  Cartesians  did  not,  is  certain.  The  case  is,  however, 
different  with  regard  to  Malebranche  and  Berkeley.  But  of  this 
again.  —  H. 


352  THE  PHILOSOPHY  OF  REID.  (Cx.  VII. 

alogous  to  the  original  quantity  of  motion  in  Des 
Cartes's  physical  system.  From  these  principles,  they 
attempt  to  explain  the  phaenomena  of  the  human  under- 
standing, just  as  in  the  physical  system  the  phaenomena 
of  nature  were  to  be  explained  by  matter  and  motion. 
It  must,  indeed,  be  acknowledged,  that  there  is  great 
simplicity  in  this  system,  as  well  as  in  the  other.  There 
is  such  a  similitude  between  the  two,  as  may  be  expected 
between  children  of  the  same  father;  but,  as  the  one  has 
been  found  to  be  the  child  of  Des  Cartes,  and  not  of 
Nature,  there  is  ground  to  think  that  the  other  is  so  like- 
wise. 

That  the  natural  issue  of  this  system  is  scepticism  with 
regard  to  everything  except  the  existence  of  our  ideas, 
and  of  their  necessary  relations,  which  appear  upon  com- 
paring them,  is  evident;  for  ideas,  being  the  only  objects 
of  thought,  and  having  no  existence  but  when  we  are 
conscious  of  them,  it  necessarily  follows  that  there  is  no 
object  of  our  thought  which  can  have  a  continued  and 
permanent  existence.  Body  and  spirit,  cause  and  effect, 
time  and  space,  to  which  we  were  wont  to  ascribe  an 
existence  independent  of  our  thought,  are  all  turned  out 
of  existence  by  this  short  dilemma.  Either  these  things 
are  ideas  of  sensation  or  reflection,  or  they  are  not;  if 
they  are  ideas  of  sensation  or  reflection,  they  can  have  no 
existence  but  when  we  are  conscious  of  them;  if  they  are 
not  ideas  of  sensation  or  reflection,  they  are  words  with- 
out any  meaning.* 

Neither  Des  Cartes  nor  Locke  perceived  this  conse- 
quence of  their  system  concerning  ideas.  Bishop  Ber- 
keley was  the  first  who  discovered  it.  And  what  followed 
upon  this  discovery  ?  Why,  with  regard  to  the  material 
world,  and  with  regard  to  space  and  time,  he  admits  the 
consequence,  That,  these  things  are  mere  ideas,  and  have 


*  This  dilemma  applies  to  the  sensualism  of  Locke,  but  not  to  the 
rationalism  of  Des  Cartes. — H. 


CH.VII.]  THE  PHILOSOPHY  OF  REID.  353 

no  existence  out  in  our  minds;  but  with  regard  to  the 
existence  of  spirits  or  minds,  he  does  not  admit  the  con- 
sequence; and,  if  he  had  admitted  it,  he  must  have  been 
an  absolute  sceptic.  But  how  does  he  evade  this  conse- 
quence with  regard  to  the  existence  of  spirits  ?  The  ex- 
pedient which  the  good  Bishop  uses  on  this  occasion  is 
very  remarkable,  and  shows  his  great  aversion  to  scepti- 
cism. He  maintains  that  we  have  no  ideas  of  spirits; 
and  that  we  can  think,  and  speak,  and  reason  about 
them,  and  about  their  attributes,  without  having  any 
ideas  of  them.  If  this  is  so,  my  Lord,  what  should  hin- 
der  as_from  thinking  and  reasoning  about  bodies,  and 
their  qualities,  without  having  ideas  of  them  ?  The 
Bishop  either  did  not  think  of  this  question,  or  did  not 
think  fit  to  give  any  answer  to  it.  However,  we  may 
observe,  that,  in  order  to  avoid  scepticism,  he  fairly  starts 
out  of  the  Cartesian  system,  without  giving  any  reason 
why  he  did  so  in  this  instance,  and  in  no  other.  This, 
indeed,  is  the  only  instance  of  a  deviation  from  Cartesian 
principles  which  I  have  met  with  in  the  successors  of 
Des  Cartes;  and  it  seems  to  have  been  only  a  sudden 
start,  occasioned  by  the  terror  of  scepticism;  for,  in  all 
other  things,  Berkeley's  system  is  founded  upon  Carte- 
sian principles. 

Thus  we  see  that  Des  Cartes  and  Locke  take  the  road 
that  leads  to  scepticism,  without  knowing  the  end  of  it; 
but  they  stop  short  for  want  of  light  to  carry  them  far- 
ther. Berkeley,  frighted  at  the  appearance  of  the  dread- 
ful abyss,  starts  aside,  and  avoids  it.  But  the  author  of 
the  "Treatise  of  Human  Nature,"  more  daring  and  in- 
trepid, without  turning  aside  to  the  right  hand  or  to  the 
left,  like  Virgil's  Alecto,  shoots  directly  into  the  gulf : 

"  Hie  specus  horrendum,  et  ssevi  spiracula  Ditis 
Monstrantur  :  ruptoque  ingens  Acheronte  vorago 
Pestiferas  aperit  fauces." 

4.  We  may  observe,  That  the  account  given  by  the 
new  system,  of  that  furniture  of  the  human  understand- 


354  THE  PHILOSOPHY   OF  REID.  [Cn.  VII. 

ing  which  is  the  gift  of  Nature,  and  not  the  acquisition 
of  our  own  reasoning  faculty,  is  extremely  lame  and  im- 
perfect* 

The  natura.  furniture  of  the  human  understanding  is 
of  two  kinds:  First,  The  notions  or  simple  apprehen- 
sions which  we  have  of  things;  and,  secondly,  The  judg- 
ments or  the  belief  which  we  have  concerning  them.  As 
to  our  notions,  the  new  system  reduces  them  to  two 
classes — ideas  of  sensation,  and  ideas  of  reflection  :  the 
first  are  conceived  to  be  copies  of  our  sensations,  re- 
tained in  the  memory  or  imagination;  the  second,  to  be 
copies  of  the  operations  of  our  minds  whereof  we  are 
conscious,  in  like  manner  retained  in  the  memory  or 
imagination  :  and  we  are  taught  that  these  two  compre- 
hend all  the  materials  about  which  the  human  under- 
standing is,  or  can  be  employed.  As  to  our  judgment 
of  things,  or  the  belief  which  we  have  concerning  them, 
the  new  system  allows  no  part  of  it  to  be  the  gift  of  na- 
ture, but  holds  it  to  be  the  acquisition  of  reason,  and  to 
be  got  by  comparing  our  ideas,  and  perceiving  their 
agreements  or  disagreements.  f  Now  I  take  this  account, 
both  of  our  notions,  and  of  our  judgments  or  belief,  to 
be  extremely  imperfect;  and  I  shall  briefly  point  out 
some  of  its  capital  defects. 

The  division  of  our  notions  into  ideas  of  sensation,")" 
and  ideas  of  reflection,  is  contrary  to  all  rules  of  logic; 
because  the  second  member  of  the  division  includes  the 
first.  For,  can  we  form  clear  and  just  notions  of  our 
sensations  any  other  way  than  by  reflection  ?  Surely  we 
cannot.  Sensation  is  an  operation  of  the  mind  of  which 
we  are  conscious;  and  we  get  the  notion  of  sensation  by 
reflecting  upon  that  which  we  are  conscious  of.  In  like 
manner,  doubting  and  believing  are  operations  of  the 
mind  whereof  we  are  conscious ;  and  we  get  the  notion 

*  The  following  summary  refers  principally  to  Locke.— H. 
f  It  must  be  remembered  that  under  Sensation  Locke  and  others 
included  Perception  proper  and  Sensation  proper. — H. 


CH.VH.]  THE   PHILOSOPHY   OF   REID.  355 

of  them  by  reflecting  upon  what  we  are  conscious  of. 
The  ideas  of  sensation,  therefore,  are  ideas  of  reflection, 
as  much  as  the  ideas  of  doubting,  or  believing,  or  any 
other  ideas  whatsoever.  * 

But,  to  pass  over  the  inaccuracy  of  this  division,  it  is 
extremely  incomplete.  For,  since  sensation  is  an  opera- 
tion of  the  mind,  as  well  as  all  the  other  things  of  which 
we  form  our  notions  by  reflection,  when  it  is  asserted 
that  all  our  notions  are  either  ideas  of  sensation  or  ideas 
of  reflection,  the  plain  English  of  this  is,  That  mankind 

*  I  do  not  see  how  this  criticism  on  Locke's  division  can  be  de- 
fended, or  even  excused.  It  is  perfectly  evident  that  Reid  here  con- 
founds the  proper  ideas  of  sensation — that  is,  the  ideas  of  the  quali- 
ties of  matter,  about  which  sensation  (perception)  is  conversant — 
with  the  idea  of  sensation  itself — that  is,  the  idea  of  this  faculty  as 
an  attribute  of  mind,  and  which  is  the  object  of  a  reflex  conscious- 
ness. Nor  would  it  be  competent  to  maintain  that  Locke,  allowing 
no  immediate  knowledge  of  aught  but  of  mind  and  its  contents,  con- 
sequently reduces  all  our  faculties  to  self-consciousness,  and  thus 
abolishes  the  distinction  of  sensation  (perception)  and  reflection,  as 
separate  faculties,  the  one  conversant  with  the  qualities  of  the  exter- 
nal world,  the  other  with  the  qualities  of  the  internal.  For,  in  the 
first  place,  it  would  still  be  logically  competent,  on  the  hypothesis 
that  all  our  knowledge  is  exclusively  of  self,  to  divide  the  ideas  we 
possessed,  into  classes,  according  as  these  were  given  as  representa- 
tions of  the  non-ego  by  the  ego,  or  as  phenomena  of  the  ego  itself. 
In  the  second  place,  Reid's  criticism  does  not  admit  of  this  excuse. 
But,  in  the  third,  if  the  defence  were  valid  in  itself,  and  here  availa- 
ble, the  philosophy  of  Reid  himself  would  be  obnoxious  to  a  similar 
criticism.  For  he  makes  perception  (consequently  the  object  known 
in  perception)  an  object  of  consciousness;  but  consciousness,  in  his 
view,  is  only  of  the  phaenomena  of  mind  itself— all  consciousness  is 
to  him  self -consciousness.  Thus,  his  perception,  as  contained  under 
his  consciousness,  is  only  cognisant  of  the  ego.  With  all  this,  how- 
ever, Reid  distinguishes  perception  and  consciousness  as  special  and 
co-ordiriate  faculties;  perception  being  conversant  about  the  qualities 
of  matter,  as  suggested — that  is,  as  represented  in  the  percipient  sub- 
ject—consciousness as  conversant  about  perception  and  the  other  at- 
tributes of  mind  itself. — With  the  preceding  observations,  the  reader 
may  compare  Priestley's  "Examination,"  p.  38,  and  Stewart's 
"Philosophical  Essays,"  Note  N.— H. 


356  THE  PHILOSOPHY   OF   REID.  [Cn.  VII. 

neither  do  nor  can  think  of  anything  but  of  the  opera- 
tions of  their  own  minds.  Nothing  can  be  more  con- 
trary to  truth,  or  more  contrary  to  the  experience  of  man- 
kind. I  know  that  Locke,  while  he  maintained  this 
doctrine,  believed  the  notions  which  we  have  of  body 
and  of  its  qualities,  and  the  notions  which  we  have  of 
motion  and  of  space,  to  be  ideas  of  sensation.  But  why 
did  he  believe  this  ?  Because  he  believed  those  notions 
to  be  nothing  else  but  images  of  our  sensations.  If, 
therefore,  the  notions  of  body  and  its  qualities,  of  mo- 
tion and  space,  be  not  images  of  our  sensations,  will  it 
not  follow  that  those  notions  are  not  ideas  of  sensation  ? 
Most  certainly.* 

There  is  no  doctrine  in  the  new  system  which  more 
directly  leads  to  scepticism  than  this.  And  the  author 
of  the  "Treatise  of  Human  Nature"  knew  very  well 
how  to  use  it  for  that  purpose  ;  for,  if  you  maintain  that 
there  is  any  such  existence  as  body  or  spirit,  time  or 
place,  cause  or  effect,  he  immediately  catches  you  be- 
tween the  horns  of  this  dilemma  ;  your  notions  of  these 
existences  are  either  ideas  of  sensation,  or  ideas  of  reflec- 

*  I  may  here  notice — what  I  shall  hereafter  more  fully  advert  to — 
that  Reid's  criticism  of  Locke,  here  and  elsewhere,  proceeds  upon 
the  implication  that  the  English  philosopher  attached  the  same  re- 
stricted meaning  to  the  term  Sensation  that  he  did  himself.  But  this 
is  not  the  case.  Locke  employed  Sensation  to  denote  both  the  idee 
and  the  sentiment  of  the  Cartesians — both  the  perception  and  the 
sensation  of  Reid.  To  confound  this  distinction  was,  indeed,  wrong, 
but  this  is  a  separate  and  special  ground  of  censure,  and,  in  a  general 
criticism  of  Locke's  doctrine,  the  fact  that  he  did  so  confound  percep- 
tion proper  and  sensation  proper,  should  always  be  taken  into  ac- 
count. But,  waving  this,  what  is  gained  by  the  distinction  in  Reid's 
hands?  In  his  doctrine,  space,  motion,  &c.,  as  perceived,  are  only 
conceptions;  only  modifications  of  self,  suggested,  in  some  unknown 
way,  on  occasion  of  the  impression  made  on  the  sense;  consequently, 
in  the  one  doctrine  as  in  the  other,  what  is  known  is  nothing  beyond 
the  affections  of  the  thinking  subject  itself;  and  this  is  the  only  basis 
required  by  the  idealist  and  sceptic  for  the  foundation  of  their  sys- 
tems.—H. 


CH.  VII.]  THE  PHILOSOPHY  OF  REID.  357 

tion  :  if  of  sensation,  from  what  sensation  are  they 
copied  ?  if  of  reflection,  from  what  operation  of  the  mind 
are  they  copied  ? 

It  is  indeed  to  be  wished  that  those  who  have  written 
much  about  sensation,  and  about  the  other  operations 
of  the  mind,  had  likewise  thought  and  reflected  much, 
and  with  great  care,  upon  those  operations  :  but  is  it 
not  very  strange  that  they  will  not  allow  it  to  be  possi- 
ble for  mankind  to  think  of  anything  else  ? 

The  account  which  this  system  gives  of  our  judgment 
and  belief  concerning  things,  is  as  far  from  the  truth  as 
the  account  it  gives  of  our  notions  or  simple  apprehen- 
sions. It  represents  our  senses  as  having  no  other  office 
but  that  of  furnishing  the  mind  with  notions  or  simple 
apprehensions  of  things  ;  and  makes  our  judgment  and 
belief  concerning  those  things  to  be  acquired  by  com- 
paring our  notions  together,  and  perceiving  their  agree- 
ments or  disagreements. 

We  have  shewn,  on  the  contrary,  that  every  operation 
of  the  senses,  in  its  very  nature,  implies  judgment  or  be- 
lief, as  well  as  simple  apprehension.  Thus,  when  I  feel 
the  pain  of  the  gout  in  my  toe,  I  have  not  only  a  notion 
of  pain,  but  a  belief  of  its  existence,  and  a  belief  of  some 
disorder  in  my  toe  which  occasions  it ;  and  this  belief 
is  not  produced  by  comparing  ideas,  and  perceiving  their 
agreements  and  disagreements  ;  it  is  included  in  the  very 
nature  of  the  sensation.  When  I  perceive  a  tree  before 
me,  my  faculty  of  seeing  gives  me  not  only  a  notion  or 
simple  apprehension  of  the  tree,  but  a  belief  of  its  exist- 
ence, and  of  its  figure,  distance,  and  magnitude  ;  and 
this  judgment  or  belief  is  not  got  by  comparing  ideas,  it 
is  included  in  the  very  nature  of  the  perception.  We 
have  taken  notice  of  several  original  principles  of  belief 
in  the  course  of  this  inquiry;  and  when  other  faculties  of 
the  mind  are  examined,  we  shall  find  more,  which  have 
not  occurred  in  the  examination  of.the  five  senses. 

Such  original  and  natural  judgments  are,  therefore,  a 


358  THE  PHILOSOPHY   OF   REID.  [Cn.  VII. 

part  of  that  furniture  which  Nature  hath  given  to  the 
human  understanding.  They  are  the  inspiration  of  the 
Almighty  no  less  than  our  notions  or  simple  apprehen- 
sions. They  serve  to  direct  us  in  the  common  affairs  of 
life,  where  our  reasoning  faculty  would  leave  us  in  the 
dark.  They  are  a  part  of  our  constitution  ;  and  all  the 
discoveries  of  our  reason  are  grounded  upon  them. 
They  make  up  what  is  called  the  common  sense  of  man- 
kind /*  and,  what  is  manifestly  contrary  to  any  of  those 
first  principles,  is  what  we  call  absurd.  The  strength  of 
them  is  good  sense,  which  is  often  found  in  those  who 
are  not  acute  in  reasoning.  A  remarkable  deviation 
from  them,  arising  from  a  disorder  in  the  constitution, 
is  what  we  call  lunacy  ;  as  when  a  man  believes  that  he 
is  made  of  glass.  When  a  man  suffers  himself  to  be 
reasoned  out  of  the  principles  of  common  sense,  by 
metaphysical  arguments,  we  may  call  this  metaphysical 
lunacy ;  which  differs  from  the  other  species  of  the  dis- 
temper in  this,  that  it  is  not  continued,  but  intermittent: 
it  is  apt  to  seize  the  patient  in  solitary  and  speculative 
moments  :  but,  when  he  enters  into  society,  Common 
Sense  recovers  her  authority,  f  A  clear  explication  and 
enumeration  of  the  principles  of  common  sense,  is  one 
of  the  chief  desiderata  in  logic.  We  have  only  consid- 
ered such  of  them  as  occurred  in  the  examination  of  the 
five  senses. 

5.  The  last  observation  that  I  shall  make  upon  the 
new  system,  is,  that,  although  it  professes  to  set  out  in 
the  way  of  reflection,  and  not  of  analogy,  it  hath  retained 
some  of  the  old  analogical  notions  concerning  the  op- 
erations of  the  mind  ;  particularly,  that  things  which  do 
not  now  exist  in  the  mind  itself,  can  only  be  perceived, 

*  See  Note  A.— H. 

f  No  one  admits  this  more  promptly  than  the  sceptic  himself. 
See  Hume's  "Treatise  of  Human  Nature,"  Book  I.,  Part  iv.,  §7, 
and  "Enquiry  Concerning  Human  Understanding,"  §  12,  Part  II. 
— H. 


CH.  VII.]  THE  PHILOSOPHY   OF   REID.  359 

remembered,  or  imagined,  by  means  of  ideas  or  images  * 
of  them  in  the  mind,  which  are  the  immediate  objects  of 
perception,  remembrance,  and  imagination.  This  doc- 
trine appears  evidently  to  be  borrowed  from  the  old  sys- 
tem ;  which  taught  that  external  things  make  impres- 
sions upon  the  mind,  like  the  impressions  of  a  seal  upon 
wax  ;  that  it  is  by  means  of  those  impressions  that  we 
perceive,  remember,  or  imagine  them  ;  and  that  those 
impressions  must  resemble  the  things  from  which  they 
are  taken.  When  we  form  our  notions  of  the  operations 
of  the  mind  by  analogy,  this  way  of  conceiving  them 
seems  to  be  very  natural,  and  offers  itself  to  our  thoughts  ; 
for,  as  everything  which  is  felt  must  make  some  im- 
pression upon  the  body,  we  are  apt  to  think  that  every- 
thing which  is  understood  must  make  some  impression 
upon  the  mind. 

From  such  analogical  reasoning,  this  opinion  of  the 
existence  of  ideas  or  images  of  things  in  the  mind,  seems 
to  have  taken  its  rise,  and  to  have  been  so  universally 
received  among  philosophers.  It  was  observed  already, 
that  Berkeley,  in  one  instance,  apostatizes  from  this  prin- 
ciple of  the  new  system,  by  affirming  that  we  have  no 
ideas  of  spirits,  and  that  we  can  think  of  them  immedi- 
ately, without  ideas.  But  I  know  not  whether  in  this 
he  has  had  any  followers.  There  is  some  difference, 
likewise,  among  modern  philosophers  with  regard  to  the 
ideas  or  images  by  which  we  perceive,  remember,  or 
imagine  sensible  things.  For,  though  all  agree  in  the 
existence  of  such  images, f  they  differ  about  their 
place  ;  some  placing  them  in  a  particular  part  of  the 

*  That  is,  by  representative  entities  different  from  the  modes  of 
the  mind  itself.  This  doctrine,  I  have  already  noticed,  is  attributed 
by  Reid  too  universally  to  philosophers;  and  is  also  a  comparatively 
unimportant  circumstance  in  reference  to  the  Idealist  and  Sceptic. 
See  Note  C.  - H. 

f  See  last  note.  Berkeley  did  hold  the  hypothesis  of  ideas  as  un- 
derstood by  Reid.— H. 


360  THE  PHILOSOPHY   OF  REID.  [Cn.  VII. 

brain,  where  the  soul  is  thought  to  have  her  residence, 
and  others  placing  them  in  the  mind  itself.  Des  Cartes 
held  the  first  of  these  opinions  ;*  to  which  Newton  seems 
likewise  to  have  inclined  ;  for  he  proposes  this  query  in 
his  "Optics:" — "Annon  sensorium  animalium  est 
locus  cui  substantia  sentiens  adest,  et  in  quern  sensibiles 
rerum  species  per  nervos  et  cerebrum  deferuntur,  ut  ibi 
praesentes  a  praesente  sentiri  possint  ?  "  But  Locke  seems 
to  place  the  ideas  of  sensible  things  in  the  mind  ;  f  and 
that  Berkeley,  and  the  author  of  the  "Treatise  of  Human 
Nature,"  were  of  the  same  opinion,  is  evident.  The 
last  makes  a  very  curious  application  of  this  doctrine, 
by  endeavouring  to  prove  from  it,  That  the  mind  either 
is  no  substance,  or  that  it  is  an  extended  and  divisible 
substance ;  because  the  ideas  of  extension  cannot  be  in 
a  subject  which  is  indivisible  and  unextended. 

I  confess  I  think  his  reasoning  in  this,  as  in  most 
cases,  is  clear  and  strong.  For  whether  the  idea  of  ex- 
tension be  only  another  name  for  extension  itself,  as 
Berkeley  and  this  author  assert ;  or  whether  the  idea  of 
extension  be  an  image  and  resemblance  of  extension,  as 
Locke  conceived  ;  I  appeal  to  any  man  of  common 
sense,  whether  extension,  or  any  image  of  extension,  can 
be  in  an  unextended  and  indivisible  subject.  But  while 
I  agree  with  him  in  his  reasoning,  I  would  make  a  differ- 
ent application  of  it,  He  takes  it  for  granted,  that  there 
are  ideas  of  extension  in  the  mind  ;  and  thence  infers, 
that,  if  it  is  at  all  a  substance,  it  must  be  an  extended 


*  An  unqualified  error,  arising  from  not  understanding  the  am- 
biguous language  of  Des  Cartes;  who  calls,  by  the  common  name 
of  ideas,  both  the  organic  motions  in  the  brain,  of  which  the  mind, 
in  his  doctrine,  necessarily  knows  nothing,  and  the  representations 
in  the  mind  itself,  hyperphysically  determined  on  occasion  of  those 
motions,  and  of  which  alone  the  mind  is  cognizant.  But  of  this  un- 
der the  "  Essays  on  the  Intellectual  Powers." — H. 

f  Locke's  opinion  on  this  point  is  as  obscure  and  doubtful  as  that 
of  Des  Cartes  is  clear  and  certain.  But  Reid  is  probably  right.— H, 


CH.  VII.]  THE  PHILOSOPHY  OF  REID.  361 

and  divisible  substance.  On  the  contrary,  I  take  it  for 
granted,  upon  the  testimony  of  common  sense,  that  my 
mind  is  a  substance — that  is,  a  permanent  subject  of 
thought ;  and  my  reason  convinces  me  that  it  is  an  un- 
extended  and  indivisible  substance  ;  and  hence  I  infer 
that  there  cannot  be  in  it  anything  that  resembles  ex- 
tension. If  this  reasoning  had  occurred  to  Berkeley,  it 
would  probably  have  led  him  to  acknowledge  that  we 
may  think  and  reason  concerning  bodies,  without  having 
ideas  of  them  in  the  mind,  as  well  as  concerning  spirits. 

I  intended  to  have  examined  more  particularly  and 
fully  this  doctrine  of  the  existence  of  ideas  or  images  of 
things  in  the  mind  ;  and  likewise  another  doctrine, 
which  is  founded  upon  it — to  wit,  That  judgment  or  be- 
lief is  nothing  but  a  perception  of  the  agreement  or  dis- 
agreement of  our  ideas  ;  but,  having  already  shewn, 
through  the  course  of  this  inquiry,  that  the  operations 
of  the  mind  which  we  have  examined,  give  no  counte- 
nance to  either  of  these  doctrines,  and  in  many  things 
contradict  them,  I  have  thought  it  proper  to  drop  this 
part  of  my  design.  It  may  be  executed  with  more  ad- 
vantage, if  it  is  at  all  necessary,  after  inquiring  into  some 
other  powers  of  the  human  understanding. 

Although  we  have  examined  only  the  five  senses,  and 
the  principles  of  the  human  mind  which  are  employed 
about  them,  or  such  as  have  fallen  in  our  way  in  the 
course  of  this  examination,  we  shall  leave  the  further 
prosecution  of  this  inquiry  to  future  deliberation.  The 
powers  of  memory,  of  imagination,  of  taste,  of  reason- 
ing, of  moral  perception,  the  will,  the  passions,  the 
affections,  and  all  the  active  powers  of  the  soul,  present 
a  vast  and  boundless  field  of  philosophical  disquisition, 
which  the  author  of  this  inquiry  is  far  from  thinking 
himself  able  to  survey  with  accuracy.  Many  authors  of 
ingenuity,  ancient  and  modern,  have  made  excursions 
into  this  vast  territory,  and  have  communicated  useful 
observations:  but  there  is  reason  to  believe  that  those 


362  THE  PHILOSOPHY  OF  REID.  [Cn.  VII. 

who  have  pretended  to  give  us  a  map  of  the  wnole,  have 
satisfied  themselves  with  a  very  inaccurate  and  incom- 
plete survey.  If  Galileo  had  attempted  a  complete  sys- 
tem of  natural  philosophy,  he  had,  probably,  done  little 
service  to  mankind:  but  by  confining  himself  to  what 
was  within  his  comprehension,  he  laid  the  foundation  of 
a  system  of  knowledge,  which  rises  by  degrees,  and  does 
honour  to  the  human  understanding.  Newton,  building 
upon  this  foundation,  and,  in  like  manner,  confining 
his  inquiries  to  the  law  of  gravitation  and  the  properties 
of  light,  performed  wonders.  If  he  had  attempted  a 
great  deal  more,  he  had  done  a  great  deal  less,  and  per- 
haps nothing  at  all.  Ambitious  of  following  such  great 
examples,  with  unequal  steps,  alas  !  and  unequal  force, 
we  have  attempted  an  inquiry  only  into  one  little  corner 
of  the  human  mind — that  corner  which  seems  to  be  most 
exposed  to  vulgar  observation,  and  to  be  most  easily 
comprehended;  and  yet,  if  we  have  delineated  it  justly, 
it  must  be  acknowledged  that  the  accounts  heretofore 
given  of  it  were  very  lame,  and  wide  of  the  truth. 


INDEX. 


Addison,  conception  of  col- 
or, 178-9. 

Agnolonius,  hiso  ptics,  254. 

Analogy,  339. 

Analysis,  of  the  human  fac- 
ulties necessary,  75-6. 

Anatomy,  mental,  72-3. 

Anepigraphus,  J.  R.,  206. 

Animal  spirits,  theory  of, 
280. 

Animals,  laws  of  vision  in, 
246. 

Apprehension,    simple,    95, 

95  H. 

Aquapendens,  284. 
Aristotle,   on    primary    and 

secondary  qualities,  140, 
156  ;  on  imagination,  182 
H.;  compared  with  Ba- 
con>  335  I  definition  of 
the  soul,  342-3  ;  referred 
to,  344;  materialistic  ten- 
dency of  his  system,  346. 
Association  of  ideas,  332-3. 

Bacon,  his  services,  334. 

Belief,  Locke's  theory  of, 
criticised,  95  sq.;  Hume's 
theory  of,  criticised, 96  sq., 
330  ;  cannot  be  defined, 

96  sq. ;     in    human    testi- 
mony, 323  sq.;  in  the  con- 
tinuance   of    the    present 
course  of  nature,  328  sq.; 
an    ingredient   of    mental 
operations,    137  sq.,     228, 
330. 


Berkeley,  relation  of  his 
philosophy  to  scepticism, 
81  sq.,  86  sq.,  349,  353  ; 
ideas  and  spirits,  102,  186; 
natural  signs,  139  H. ;  pri- 
mary and  secondary  qual- 
ities of  matter,  140  ;  qual- 
ities of  matter  not  resem- 
bling sensations,  138  sq., 
J53>  r58;  his  solution  of 
certain  phenomena  of  vi- 
sion examined,  218,  220 
sq.  ;  noticed,  148,  160, 
186,  199 H.,  267,  272,  310, 
312,  316,  345. 

Body,  its  qualities,  how  ap- 
prehended, 181  sq. 

Borrichius,  210. 

Brain,  223,  224. 

Briggs,  Dr.,  254,  279. 

Caesalpinus,  284. 

Cause  and  effect,  332. 

Cheselden,  case  of  couch- 
ing, 172,  194,  271  sq.;  on 
double  vision,  270. 

Cold,  I29sq. ;  see  Touch. 

Color,  162  sq. ;  see  Seeing;  a 
blind  man's  notion  of, 
165  sq. 

Common  sense,  the  root  of 
all  philosophy,  81  ;  prin- 
ciples of,  100,  358  ;  prac- 
tically acknowledged  by 
the  idealists,  104  ;  con- 
trasted with  the  ideal  phi- 
losophy, 132  sq.,  358. 

363 


364 


INDEX. 


Conception,  distinguished 
from  perception,  289  H. 

Consciousness,  Des  Cartes' 
view  of,  345  H.,  350. 

Credulity,  325. 

Custom,  265  sq. 

Democritus,  on  the  qualities 
of  matter,  140,  157,  180, 
i8oH. 

Des  Cartes,  his  doubt,  77, 
345  ;  misapprehended  by 
Reid,  77  H.;  scepticism 
the  natural  issue  of  his 
system,  86  sq.,  349;  on 
primary  and  secondary 
qualities,  140,  157  ;  on 
seeing  objects  erect  by  in- 
verted images,  215,  216  ; 
the  father  of  the  new 
philosophy  of  mind,  341  ; 
remarks  upon  the  Car- 
tesian system,  345  sq.  ;  no- 
ticed, 72,  82,  84,  103,  148, 
154,  155  H.,  1  60,  184. 

Dimerbroeck,  284. 

Distance,  how  computed  by 
the  eye,  304  sq. 

Divine  veracity,  155  H. 

Effluvia,  90. 


343. 

Epicurus  and  the  Epicu- 
reans, on  primary  and 
secondary  qualities,  140, 
157,  180.;  theory  of  per- 
ception, 344. 

Experience,  323. 

Experiment,   71. 

Extension,  notion  of,  141-7, 
187—91;  see  Seeing,  Sight, 
Touch;  Reid's  and  Kant's 
theories  contrasted,  141 
H.;  possibility  of  an  a 
posteriori  perception  of, 
147  H. 

Eyes,  parallel  motion  of, 
211  sq.,  265  sq.  ;  concen- 
tration on  one  object,  263 
sq.  ;  see  Seeing. 

Fabricius,  210. 


Fichte,  idealism,  152  H. 
Figure,    how    perceived    by 

the  eye,  315. 
Folkes,  Martin,  269. 
Foster,  case  of,  269,  270. 

Galen,  239. 

Gassendi,  239. 

Genius,  adulterates  phil^so- 

phy,  76. 
Geometry    of    visibles,    199 

sq. ;  see  Seeing. 
Grew,  Dr.  N.,  121. 

Halley,  Dr.,  165. 

Hardness,  131,  139  sq.;  see 
Touch. 

Hearing,   122  sq. 

Heat,  129  ;  see  Touch, 

Hobbes,  on  imagination, 
182  H.;  noticed,  84. 

Hume,  his  Treatise  of  Hu- 
man Nature  considered, 
8isq.;  reduces  Berkeley's 
system  to  scepticism,  86, 
353;  his  theory  of  belief 
examined,  96  sq.,  330;  his 
theory  of  mind,  100  sq. ; 
confession,  135,  358  H.; 
noticed,  139,  150,  160, 
184,  186,  345,  349  H,  356. 

Idea,  how  used  by  Reid, 
93-4;  by  Des  Cartes,  351, 
360. 

Idealism,   151-2  H. 

Ideal  philosophy,  87  ;  the 
theory  of  sensation,  mem- 
ory, belief,  and  imagina- 
tion introduced  by  it  con- 
sidered, 96;  psychological 
history  of,  100  sq. ;  re- 
marks on,  153  sq. 

Ideas,  doctrines  of  ancient 
philosophers  about,  343 
sq. 

Identity,  Locke's  account  of, 
considered,  79. 

Image,  Reid's  use  of  the 
term,  93. 

Imagination,  how  accom- 
panied, 93  H.;  view  of 


INDEX. 


365 


Aristotle  and  Hobbes,  182 
H.;  distinguished  from 
perception,  289  H. 

Impressions,  in  reference  to 
sensations,  298  sq. ;  on  the 
mind,  the  peripatetic 
theory  of,  347. 

Inductive  principle,  328  sq. 

Instinct,  instinctive  beliefs, 
291  sq. ;  belief  in  the  con- 
stancy of  nature,  see  In- 
ductive principle. 

Jacobi,    on    perception,  302 

H . 
Jurin,  Dr., 

Kant,  relation  to  Hume,  66 
H.;  held  the  notion  of  ex- 
tension to  be  a  priori,  141 
H.,  147  H. 

Kepler,  on  seeing  objects 
erect  by  inverted  images, 
215,  216. 

Laertius,  83. 

Language,  imperfection  of, 
impediment  to  the  study 
of  mind,  74  sq.;  natural, 
etc.,  considered,  124-8, 
136- 

Laws  of  nature,  their  char- 
acter, 225,  230  sq.,  239 
sq. ;  belong  to  mind  as 
well  as  to  matter,  225. 

Light,  162;  see  Seeing. 

Locke,  his  theory  of  person- 
al identity  considered,  79; 
his  definition  of  knowl- 
edge criticised,  97  sq.; 
quoted,  152;  his  doctrine 
of  primary  and  secondary 
qualities  discussed,  157, 
179,  185;  not  the  origina- 
tor of  these  terms,  185  H. ; 
misinterpreted  by  Reid, 
347  H. ;  noticed, '79,  82, 
103,  148,  160. 

Lucretius,  344. 

Malebranche,  his  doctrine 
of  primary  and  secondary 


qualities,  140,  157,  184, 
186;  his  theory  of  per- 
ception, 343-4;  noticed, 
79,  82,  103,  148,  160. 

Mariotte,  251. 

Memory  distinguished  from 
perception,  330;  denned, 

94- 

Metaphysic,  88. 

Mind,  importance  of  the 
study  of,  70;  how  to  be 
studied,  71,  72;  impedi- 
ments to  our  knowledge 
of,  72-6;  the  systems  of 
Des  Cartes,  Malebranche, 
and  Locke,  considered, 
76-80;  of  Berkeley  and 
Hume,  8 1-6;  its  exist- 
ence, how  inferred,  105 
sq.;  in  sensation,  act- 
ive or  passive?,  116-17; 
operations  of,  two  ways 
of  treating,  338;  names  of 
operations  borrowed  from 
sensible  images,  341. 

Nature,  the  works  of,  85; 
our  belief  in  the  uniform- 
ity of,  328  sq. 

Nerves,  theory  of,  279. 

Newton,  Sir  Isaac,  his  reg- 
ular philosophy,  71;  on 
color,  etc.,  119;  his 
query  on  single  vision, 
246,  282;  attracting  and 
repelling  forces,  218,  350; 
followed  Bacon's  rules  of 
inductive  reasoning,  335; 
concerning  species,  360; 
noticed,  113,  162,  351. 

Optic  nerve,    222,  336,   279. 

Perception,  in  general,  287- 
303;  distinguished  from 
sensation,  288,  298;  law 
of  the  manifestation  of 
sensation  and  perception, 
287  H.;  distinguished 
from  imagination,  289, 
289  H.;  from  memory, 
289;  what  it  implies,  289; 


366 


INDEX. 


original  and  acquired, 
293  sq. ;  involves  no  ex- 
ercise of  reason,  295;  per- 
ception of  objects,  the  re- 
sult of  what,  297-303; 
the  true  object  of,  im- 
mediate, 298  H.;  analo- 
gous to  testimony,  320-37. 

Peripatetics,  on  species, 
344;  their  tendency  to 
materialize  mind,  346; 
noticed,  183,  187. 

Phantasms,  344. 

Philosophers,  their  notions 
concerning  the  soul,  341. 

Plato,  his  system  of  ideas, 
343  sq.;  noticed,  104. 

Platonists,  their  notion  of 
the  soul,  344. 

Porta,  Baptista,  239. 

Porterfield,  Dr.,  on  vision, 
226,  231  239,  253,  261, 
272  sq. 

Pyrrho,  the  Elean,  83. 

Qualities,  primary  and  sec- 
ondary, the  distinction  of, 
140,  157,  iSssq.;  i8sH. 

Reason,  in  connection  with 
common  sense,  79  sq., 
149;  inaccurate  use  of 
term  by  Reid,  79  H.,  149 
H.;  in  relation  to  our  be- 
lief in  testimony,  327. 

Reflection,  338;  Locke's  ac- 
count of,  355-6. 

Retina,  how  rays  of  light 
affect,  194-237;  see  See- 
ing; how  objects  fall 
upon,  240. 

Rousseau,  336-7. 

Saunderson,  N.,  145,  165, 
188,  220. 

Scepticism,  in  philosophy  of 
Des  Cartes,  Malebranche, 
Locke,  and  Berkeley,  82, 
86  sq.,  349  sq. ;  animad- 
verted on,  290;  origin  of, 
35I-2- 


Scheiner,  experiments  ort 
the  eye,  231. 

Seeing,  in  general,  162  sq.; 
color,  173-81;  visible 
figure  and  extension,  187- 
91;  geometry  of  visibles, 
199-211;  certain  phenom- 
ena of  vision  examined: 
the  parallel  motion  of  the 
eyes,  our  seeing  objects 
erect  by  inverted  images, 
seeing  objects  single  with 
two  eyes,  211  sq. 

Sensation,  indefinable,  96; 
belongs  to  a  sentient  be- 
ing, 107;  what  it  suggests, 
106;  does  not  resemble 
qualities  of  body,  181-7; 
distinguished  from  per- 
ception, 288,  298;  sensa- 
tion and  reflection  as  the 
sources  of  ideas,  consid- 
ered, 354  sq. 

Sensations,  distinguished 
from  qualities  causing 
them,  109  sq.,  114  sq., 
129  sq.,  132  sq.,  157,  173 
sq.,  177. 

Sense,  testimony  of,  320-37. 

Senses,  systems  concerning, 
156-61;  do  not  deceive, 

3i9- 

Sensorium,  defined,  222;  the- 
ories concerning,  280-5. 

Sight,  see  Seeing. 

Sign,  connection  of,  with 
thing  signified, 135  sq. 

Smelling,  in  general,  89-116; 
the  sensation  considered 
abstractly, 90-2;  compared 
with  the  remembrance 
and  imagination,  92-5;  as 
a  quality  in  bodies,  etc., 
109-11;  the  name  of 
smell,  to  what  it  belongs, 
115-16;  in  sensation,  the 
mind  active  or  passive?, 
116-17. 

Smith,  Dr.,  his  system  of 
optics,  216,  246,  262,  267, 
268,  269,  270,  272,  275, 
279,  310,  313,  314,  316. 


INDEX. 


367 


Softness,  131  \  see  Touch. 
Soul,  opinions  regarding  its 

nature,  341  sq. 
Sound,  see  Hearing. 
Species,     sensible,  theories 

of,  1 80,  344. 
Squinting,  see  Seeing. 
Strabismus,  277. 
Suggestion,  explained,    107 

sq.,  107-8  H. 

Taste,  118-21. 
Tertullian,  108  H. 
Testimony,      evidence     of, 

compared   with     that     of 

sense,  320-37. 
Touch,    analysed,    129   sq.; 

heat  and   cold,    129    sq. ; 

hardness     and     softness, 

131     sq. ;    hardness    and 


other  primary  qualities, 
139  sq-  extension,  141 
sq.;  existence  of  a  ma- 
terial world,  148  sq. 
Truth,  an  innate  principle, 
324. 

Valverda,  284. 
Vesalius,  284. 
Virgil,  quoted,  351. 
Visibles,    geometry    of,    see 

Seeing. 
Vision,  see  Seeing. 

Winslow,  quoted,  284. 
World,    material,    existence 

of,  a  first  principle,    148- 

56,  348,  357  sq. 

Zeno.  84, 


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